U.S. patent application number 10/573979 was filed with the patent office on 2007-02-15 for method for pickling metallic surfaces by using alkoxylated alkynols.
This patent application is currently assigned to BASF Aktiengesellschaft Patents, Trademarks and Licenses. Invention is credited to Frank Dietsche, Thomas Heidenfelder, Helmut Witteler.
Application Number | 20070034606 10/573979 |
Document ID | / |
Family ID | 34424316 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070034606 |
Kind Code |
A1 |
Dietsche; Frank ; et
al. |
February 15, 2007 |
Method for pickling metallic surfaces by using alkoxylated
alkynols
Abstract
Process for pickling metallic surfaces by treating the metallic
surface with a composition which comprises water, at least one
acid, an alkyne alkoxylate and optionally further additives. In a
preferred embodiment, the alkyne alkoxylate is used together with a
complexing agent.
Inventors: |
Dietsche; Frank;
(Schriesheim, DE) ; Heidenfelder; Thomas;
(Dannstadt, DE) ; Witteler; Helmut; (Wachenheim,
DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
P O BOX 2207
WILMINGTON
DE
19899
US
|
Assignee: |
BASF Aktiengesellschaft Patents,
Trademarks and Licenses
Carl-Bosch-Strasse; GVX-C006
Ludwigshafen
DE
D-67056
|
Family ID: |
34424316 |
Appl. No.: |
10/573979 |
Filed: |
September 24, 2004 |
PCT Filed: |
September 24, 2004 |
PCT NO: |
PCT/EP04/10719 |
371 Date: |
March 30, 2006 |
Current U.S.
Class: |
216/100 |
Current CPC
Class: |
C23F 11/04 20130101;
C23G 1/06 20130101; C23G 1/088 20130101; C23C 22/08 20130101; C23G
1/08 20130101; C23G 1/068 20130101 |
Class at
Publication: |
216/100 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2003 |
DE |
10345801.8 |
Apr 20, 2004 |
DE |
102004019709.1 |
Claims
1. A process for pickling metallic surfaces comprising treating the
metallic surface with an acidic aqueous formulation which comprises
at least one acid, a pickling inhibitor and optionally further
additives, wherein the aqueous formulation comprises at least the
following components: (a) from 60 to 99.97% by weight of a mixture
of water and at least one acid, (b) from 0.01 to 2% by weight of at
least one alkyne propoxylate of the formula
HC.ident.C--CH.sub.2--O(--CH.sub.2--CH(CH.sub.3)--O--).sub.nH (I)
or
H(--O--CH(CH.sub.3)--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.sub.2--
-O(--CH.sub.2--CH(CH.sub.3)--O--).sub.n'H, (II) where the indices n
and n' independently of one another are from 1 to 10, and (c) from
0.01 to 20% by weight of at least one surface-active substance.
2. The process according to claim 1, wherein the indices n and n',
independently of one another, are from 1 to 3.
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. The process according to claim 1, wherein the pH of the
composition is from 3 to 6.
9. The process according to claim 1, wherein the acid is at least
one acid selected from the group consisting of hydrochloric acid,
sulfuric acid, methanesulfonic acid and phosphoric acid.
10. The process according to claim 1, wherein the metallic surface
is at least one surface selected from the group of consisting of
iron, steel, zinc, brass and aluminum.
11. The process according to claim 1, wherein the surface is the
surface of a strip metal.
12. A process for pickling metallic surfaces comprising treating
the metallic surface with an acidic aqueous formulation which
comprises at least one acid, a pickling inhibitor and optionally
further additives, wherein the aqueous formulation comprises at
least the following components: (d) from 60 to 99.97% by weight of
a mixture of water and at least one acid, (e) from 0.01 to 2% by
weight of at least one alkyne alkoxylate of the formula
HC.ident.C--CH.sub.2--O(--CH.sub.2--CHR.sup.1--O--).sub.nH (I) or
H(--O--CHR.sup.1--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.sub.2--O(-
--CH.sub.2--CHR.sup.1--O--).sub.nH, (II) where the radicals R.sup.1
in each case independently of one another are H or methyl and the
indices n and n', independently of one another, are from 1 to 10,
(f) from 0.01 to 20% by weight of at least one surface-active
substance, and (g) from 0.01 to 10% by weight of at least one
water-soluble, at least bidentate, chelate-forming complexing agent
comprising acidic groups and/or at least one water-soluble polymer
comprising quatemized ammonium groups.
13. An acidic, aqueous composition for pickling metallic surfaces,
which comprises at least one acid, a pickling inhibitor and
optionally further additives, wherein the aqueous formulation
comprises at least the following components: (a) from 60 to 99.97%
by weight of a mixture of water and at least one acid, (b) from
0.01 to 2% by weight of at least one alkyne alkoxylate of the
formula HC.ident.C--CH.sub.2--O(--CH.sub.2--CHR.sup.1--O--).sub.nH
(I) or
H(--O--CHR.sup.1--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.sub.2--O(-
--CH.sub.2--CHR.sup.1--O--).sub.nH, (II) where the radicals R.sup.1
in each case independently of one another are H or methyl and the
indices n and n', independently of one another, are from 1 to 10,
(c) from 0.01 to 20% by weight of at least one surface-active
substance, and (d) from 0.01 to 10% by weight of at least one
water-soluble, at least bidentate, chelate-forming complexing agent
comprising acidic groups and/or at least one water-soluble polymer
comprising quatemized ammonium groups.
14. The composition according to claim 13, wherein the aqueous
formulation has the following composition: (a) from 70 to 98.9% by
weight of a mixture of water and at least one acid, (b) from 0.1 to
2% by weight of alkyne alkoxylates, (c) from 0.5 to 15% by weight
of a surface-active substance, and (d) from 0.5 to 10% by weight of
a chelate-forming complexing agent and/or a polymer com
15. A process for pickling metallic surfaces comprising treating
the metallic surface with an acidic aqueous formulation which
comprises at least one acid, a pickling inhibitor and optionally
further additives, wherein the aqueous formulation comprises at
least the following components: (h) from 60 to 99.97% by weight of
a mixture of water and at least one acid, (i) from 0.01 to 2% by
weight of at least one alkyne propoxylate of the formula
HC.ident.C--CH.sub.2--O(--CH.sub.2--CH(CH.sub.3)--O--).sub.nH (I)
or
H(--O--CH(CH.sub.3)--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.sub.2--
-O(--CH.sub.2--CH(CH.sub.3)--O--).sub.n'H, (II) where the indices n
and n' independently of one another are from 1 to 10, (j) from 0.01
to 10% by weight of at least one water-soluble, at least bidentate,
chelate-forming complexing agent comprising acidic groups and/or at
least one water-soluble polymer comprising quatemized ammonium
groups.
16. The process according to claim 15, wherein the weight ratio of
complexing agent to pickly inhibitor is form 5:1 to 1:10.
17. The process according to claim 12, wherein the weight ratio of
complexing agent to pickling inhibitor is form 5:1 to 1:10.
18. The process according to claim 15, wherein the indices n and
n', independently of one another, are from 1 to 3.
19. The process according to claim 12, wherein the indices n and
n', independently of one another, are from 1 to 3.
20. The process according to claim 15, wherein the PH of the
composition is from 3 to 6.
Description
[0001] The present Application relates to a process for pickling
metallic surfaces by treating the metallic surface with a
composition which comprises water, at least one acid, an alkyne
alkoxylate and optionally further additives. In a preferred
embodiment, the alkyne alkoxylate is used together with a
complexing agent.
[0002] In pickling, the surface of a material is treated with a
pickle and thus changed by a chemical method. Here, undesired
surface layers are removed and, if appropriate, protective or
effect layers are built up. In the case of metallic surfaces,
pickling serves in particular for removing various oxide layers,
for example rust or scale layers, and/or other impurities, for
example greases, oils or lime, from the surface and/or for
activating and/or protecting the surface. An example of a
protective treatment is an acidic phosphating of an iron or steel
surface. Here too, a substantial element is a pickle attack on the
metal. In phosphating with an acidic zinc phosphate solution, a
large number of H.sup.+ ions are consumed directly at the metal
surface through the pickle attack of the acid on the metal,
producing a local increase in the pH. Only as a result of this is
the solubility product with zinc phosphate exceeded so that zinc
phosphate is deposited in a thin layer on the surface.
[0003] Aqueous, inorganic or organic acids, in particular
hydrochloric acid, phosphoric acid or sulfuric acid, and as a rule
assistants, for example surfactants, are used for pickling.
Although the acid is intended to attack the surface layers and, if
appropriate, also the metal itself, it is as a rule undesirable if
excessive amounts of metal are dissolved. On the one hand, a great
deal of pickling acid is consumed thereby and the pickle is
contaminated with dissolved metal ions. The pickling bath must
accordingly frequently be renewed. On the other hand, however, the
surface--in particular in the case of iron or nickel--may also be
damaged by so-called hydrogen embrittlement. Pickling inhibitors
which are intended to prevent or at least greatly slow down the
dissolution of the base metal without substantially hindering the
dissolution of the surface layers are therefore usually added to
formulations for pickling. Pickling with the use of inhibitors is
also occasionally referred to as inhibited pickling.
[0004] It is known that alkynols, for example 2-butyne-1,4-diol,
1-propyn-3-ol or 1-ethynyl-cyclohexanol, can be used as pickling
inhibitors. By way of example, reference may be made to U.S. Pat.
No. 3,658,720, U.S. Pat. No. 3,969,260 or JP-A 60-208 487. WO
99/32687 discloses the use of 2-butyne-1,4-diol as an inhibitor in
the acidic phosphating of steel strip galvanized on one side.
[0005] When handling alkynols, particular caution must be
exercised. 2-Butyne-1,4-diol and 1-propyn-3-ol are classified as
toxic and carcinogenic, respectively.
[0006] Alkyne alkoxylates are in principle known, for example from
DE-A 22 41 155. They are used, inter alia, as bright electroplating
additives in the electroplating of nickel or cobalt, as disclosed
in U.S. Pat. Nos. 3,804,727, 3,814,674 or U.S. Pat. No. 4,832,802.
Alkoxylated alkynols are not classified as toxic or
carcinogenic.
[0007] U.S. Pat. No. 3,004,925 discloses the use of ethoxylated
butynediol derivatives and ethoxylated propynol derivatives as a
corrosion inhibitor in aqueous solutions. The OH groups are in each
case modified with --(CH.sub.2--CH.sub.2O).sub.x, groups, where x
has a value of from 3 to 25. Furthermore, the disclosed alkynols
additionally have one or more alkyl, aryl, cycloalkyl and aralkyl
groups. Unsubstituted butynediol or propargyl alcohol is not
disclosed.
[0008] U.S. Pat. No. 5,215,675 discloses compositions for removing
finishes from surfaces, which comprise from 10 to 50% of water,
from 3 to 15% of a peroxide and from 40 to 70% of ethyl lactate.
The composition may furthermore optionally also comprise
ethoxylated butynediol as a corrosion inhibitor, and an acid. In a
further embodiment, a composition which comprises 55 to 60% of
butyrolactone, from 30 to 32% of aqueous hydrogen peroxide, 9.5% of
formic acid, 1% of ethoxylated butanediol, 0.5% of Na.sub.4EDTA and
4% of surfactant is disclosed.
[0009] It is an object of the present invention to provide a
process for pickling metallic surfaces, in which butynediol or
propynol are replaced by suitable substitutes, and in which better
pickling inhibition is nevertheless achieved. We have found that
this object is achieved by a process for pickling metallic
surfaces, in which the metallic surface is treated with an acidic
aqueous formulation which comprises at least the following
components: [0010] (a) from 60 to 99.99% by weight of a mixture of
water and at least one acid, [0011] (b) from 0.01 to 2% by weight
of at least one alkyne alkoxylate of the formula
HC.ident.C--CH.sub.2--O(--CH.sub.2--CHR.sup.1--O--).sub.nH or
H(--O--CHR.sup.1--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.sub.2--O(-
--CH.sub.2--CHR.sup.1--O--).sub.n'H, where the radicals R.sup.1 in
each case independently of one another are H or methyl and the
indices n and n', independently of one another, are from 1 to 10,
and [0012] (c) from 0 to 38% by weight of one or more additives
and/or assistants.
[0013] In a preferred embodiment, the pickling inhibitor is used in
combination with a water-soluble complexing agent.
[0014] Regarding the invention, the following may be stated
specifically:
[0015] The novel process can in principle be used for pickling
metallic surfaces of various types. The metals may be pure metals
as well as alloys. Examples comprise surfaces of iron, cast iron,
steel, nickel, zinc, brass or aluminum, and in each case the top
metal layer, which is in direct contact with the formulation, is
meant. The metallic surface may also be, for example,
surface-hardened steel, such as hot-galvanized and zinc-plated
steels. The process is particularly suitable for pickling surfaces
of (cast) iron, steel or aluminum, very particularly preferably for
steel surfaces. The process is particularly suitable for pickling
surfaces of strip metals, for example for steel or aluminum.
[0016] The metallic surfaces may be outer surfaces of metallic
materials, for example the surface of metallic strips, sheets or
irregularly shaped workpieces, such as machine parts. However, they
may also be inner surfaces, such as the inner surfaces of
pipelines, boilers, chemical plants or the like.
[0017] In the novel pickling process, undesired surface layers and
impurities are removed and, if appropriate, protective and/or
effect layers are built up. The term pickling includes the
phosphating of metallic surfaces. Undesired surface layers may be
in particular inorganic layers, for example substantially oxidic
layers, such as rust layers, scale layers or layers which are
formed in the rolling of metals, for example of steel. They may
also be layers applied for temporary corrosion protection, for
example phosphate layers or layers of other materials, for example
carbonate layers, such as lime layers or patinas. Undesired layers
may furthermore be thin layers of organic materials, for example
grease or oil layers.
[0018] The formulation used for the novel process comprises, as
component (a), water and at least one acid, together in an amount
of 60-99.99% by weight. The stated percentages here and below are
always based on the amount of all components of the
formulation.
[0019] The total amount of water and acid is preferably from 70 to
99.99%, very particularly preferably from 80 to 99.99, % by
weight.
[0020] The acid may be an inorganic acid, for example hydrochloric
acid, hypochlorous and chlorous acid, sulfuric acid, phosphoric
acid or phosphorous acid, or an organic acid, for example formic
acid, methanesulfonic acid, acetic acid, citric acid, succinic acid
or amidosulfonic acid. Of course, mixtures of different acids may
also be used, for example mixtures of hydrochloric acid and
phosphoric acid. The acid is preferably hydrochloric acid, sulfuric
acid, methanesulfonic acid or phosphoric acid.
[0021] The respective amount of water and acid depends on the one
hand on the intended use of the formulation and also on the type of
acid. Whereas, with the use of phosphoric acid, the solvent can in
particular cases consist exclusively of concentrated (i.e. 85%
strength) phosphoric-acid, greater dilutions are advantageous with
the use of acids other than phosphoric acids. If acids other than
phosphoric acid are used, the formulation comprises, as a rule, at
least 50, preferably at least 60, % by weight of water. The total
amount of water in the formulation is calculated here as the sum of
the water which is added together with the acid and that which is
added in pure form or in the form of solutions or other
materials.
[0022] The component (b) in the formulation used for the novel
process comprises from 0.01 to 2% by weight of at least one alkyne
alkoxylate of the formula
HC.ident.C--CH.sub.2--O(--CH.sub.2--CHR.sup.1--O--).sub.nH (I) or
H(--O--CHR.sup.1--CH.sub.2--).sub.n--O--CH.sub.2--C.ident.C--CH.s-
ub.2--O(--CH.sub.2--CHR.sup.1--O--).sub.n'H (II).
[0023] The indices n and n', independently of one another, are from
1 to 10. It is known to a person skilled in the art that such
alkoxy groups are obtainable in particular by oxyalkylation or
starting from industrial polyglycols. Said values for n are
therefore average chain lengths, where the average value need not
of course be a natural number but may also be any desired rational
number. n and n' are preferably a number from 1 to 3.
[0024] The radicals R.sup.1 in (I) and (II) are in each case
independently of one another H or methyl. The alkyleneoxy groups
may be groups derived exclusively from ethylene oxide units or
groups derived exclusively from propylene oxide. However, they may
also be groups which have both ethylene oxide units and propylene
oxide units.
[0025] Polyoxypropylene units are preferred
[0026] Of course, mixtures of (I) and (II) and/or mixtures of
different compounds (I) or different compounds (II) may also be
used. Compound (I) is preferably used.
[0027] From 0.05 to 2% by weight of (I) and/or (II) are preferably
used, particularly preferably from 0.075 to 1.5, very particularly
preferably from 0.1 to 1.0, % by weight. All concentration data are
based on the ready-to-use composition. It is of course possible
first to prepare concentrate, which is diluted to the desired
concentration only on site.
[0028] The amount of (I) and/or (II) also depends on the type and
amount of the acid used and on the temperature at which the
formulation is to be used. The higher the acid concentration, the
higher the concentration of pickling inhibitor (I) and/or (II) used
in each case should generally also be. The higher the temperature,
the higher the concentration of pickling inhibitor should also
generally be. The amounts stated below have proven particularly
useful for use at room temperature: TABLE-US-00001 Amount of acid
[% by Pickling inhibitor [% by weight] weight] 5 0.03-0.1 10
0.05-0.2 15 0.1-0.3 20 0.15-0.4
[0029] The compounds used are obtainable in a known manner by
oxyalkylation of butynediol or propargyl alcohol, as described, for
example, in DE-A 22 41 155 or U.S. Pat. No. 3,814,674.
[0030] The formulation used for the process furthermore comprises,
as a rule, one or more additives or assistants, even if the
addition thereof is not absolutely essential in every case.
[0031] The amount of such additives is from 0 to 38, preferably
from 0.01 to 30, particularly preferably from 0.1 to 20, % by
weight.
[0032] Assistants comprise in particular from 0.01 to 20% by weight
of at least one surface-active substance. Preferably from 0.1 to
10, particularly preferably from 0.5 to 8, % by weight of the
surface-active substance are used. Examples of suitable
surface-active substances comprise conventional anionic, cationic
or nonionic surfactants.
[0033] Particularly suitable nonionic surfactants are: [0034]
Alkoxylated C.sub.8-C.sub.22-alcohols, such as fatty alcohol
alkoxylates, oxo alcohol alkoxylates and Guerbet alcohol
ethoxylates: the alkoxylation can be effected with ethylene oxide,
propylene oxide and/or butylene oxide. Block copolymers or random
copolymers may be present. They usually comprise from 2 to 50,
preferably from 3 to 20, mol of at least one alkylene oxide per
mole of alcohol. The preferred alkylene oxide is ethylene oxide.
The alcohols preferably have 10 to 18 carbon atoms. [0035]
Alkylphenol alkoxylates, in particular alkylphenol ethoxylates,
which comprise C.sub.6-C.sub.14-alkyl chains and from 5 to 30 mol
of alkylene oxide/mole. [0036] Alkylpolyglucosides which comprise
C.sub.8-C.sub.22-alkyl, preferably C.sub.10-C.sub.18-alkyl, chains
and as a rule from 1 to 20, preferably from 1.1 to 5, glucoside
units. [0037] N-Alkylglucamides, fatty acid-amide alkoxylates,
fatty acid alkanolamide alkoxylates and block copolymers of
ethylene oxide, propylene oxide and/or butylene oxide.
[0038] Examples of suitable anionic surfactants are: [0039]
Sulfates of (fatty) alcohols of 8 to 22, preferably 10 to 18,
carbon atoms, in particular C.sub.9C.sub.11-alcohol sulfates,
C.sub.12C.sub.14-alcohol sulfates, C.sub.12-C.sub.18-alcohol
sulfates, lauryl sulfate, cetyl sulfate, myristyl sulfate, palmityl
sulfate, stearyl sulfate and tallow fatty alcohol sulfate. [0040]
Sulfated alkoxylated C.sub.8-C.sub.22-alcohols (alkyl ether
sulfates): compounds of this type are prepared, for example, by
first alkoxylating a C.sub.8-C.sub.22-alcohol, preferably a
C.sub.10-C.sub.18-alcohol, e.g. a fatty alcohol, and then sulfating
the alkoxylation product. Ethylene oxide is preferably used for the
alkoxylation. [0041] Linear C.sub.8-C.sub.20-alkylbenzenesulfonates
(LAS), preferably linear C.sub.9-C.sub.13-alkyl-benzenesulfonates
and -alkyltoluenesulfonates. [0042] Alkanesulfonates, in particular
C.sub.8-C.sub.24-alkanesulfonates, preferably
C.sub.10-C.sub.18-alkanesulfonates. [0043] Soaps, such as the Na
and K salts of C.sub.8-C.sub.24-carboxylic acids.
[0044] The anionic surfactants are preferably added in the form of
salts. Suitable cations are, for example, alkali metal ions, such
as sodium, potassium and lithium, and ammonium salts, such as
hydroxyethylammonium, di(hydroxyethyl)ammonium and
tri(hydroxyethyl)ammonium salts.
[0045] Examples of particularly suitable cationic surfactants are:
[0046] C.sub.7-C.sub.25-alkylamines; [0047]
N,N-dimethyl-N-(hydroxy-C.sub.7-C.sub.25-alkyl)ammonium salts;
[0048] mono- and di-(C.sub.7-C.sub.25-alkyl)dimethylammonium
compounds quaternized with alkylating agents; [0049] ester quats,
in particular quaternized esterified mono-, di- and
trialkanolamines which have been esterified with
C.sub.8-C.sub.22-carboxylic acids; [0050] imidazoline quats, in
particular 1-alkylimidazolinium salts of the formulae III or IV
##STR1## [0051] where [0052] R.sup.2 is C.sub.1-C.sub.25-alkyl or
C.sub.2-C.sub.25-alkenyl; [0053] R.sup.3 is C.sub.1-C.sub.4-alkyl
or hydroxy-C.sub.1-C.sub.4-alkyl; [0054] R.sup.4 is
C.sub.1-C.sub.4-alkyl, hydroxy-C.sub.1-C.sub.4-alkyl or a radical
R.sup.4 --(CO)--X--(CH.sub.2).sub.p--(X:--O-- or --NH--; p: 2 or
3), [0055] at least one radical R.sup.2 being
C.sub.7-C.sub.22-alkyl.
[0056] Of course, a plurality of different surfactants may also be
used. A person skilled in the art makes a suitable choice from
among the surface-active substances depending on the desired
application. Proposed formulations are described in the relevant
literature, for example the technical information from BASF AG,
Technische Reinigungsmittel, January 1993 edition.
[0057] Nonionic surfactants are preferably used.
[0058] The formulation used particularly preferably comprises one
or more water-soluble complexing agents as further components. The
complexing agents have a synergistic effect together with the
pickling inhibitor. It has been found that, when added to pickling
acids, complexing agents accelerate the removal of metal. If,
however, they are used in combination with the alkoxylated alkynols
employed as pickling inhibitors in accordance with the invention,
the inhibiting effect of the pickling inhibitor is not reduced by
the complexing agent but on the contrary is even enhanced. In
experiments, it was possible to improve the inhibiting effect by up
to 60% by adding a complexing agent.
[0059] The complexing agent is a water-soluble, at least bidentate
ligand which is capable of forming chelate complexes. The ligand
comprises acidic groups, preferably COOH groups. As below, the
complexing agent has at least two COOH groups. A bidentate to
hexadentate ligand is preferred, and a bidentate to tetradentate
ligand is particularly preferred. A person skilled in the art knows
that the coordinating groups in a chelate-forming ligand are
arranged in such a way that the ligand together with the metal can
form one or more rings, in particular five-membered rings.
[0060] The-ligand can moreover comprise other atoms or groups which
are capable of forming coordinate bonds to metal ions. Examples of
these are in particular OH groups and nitrogen-containing groups,
such as primary, secondary and tertiary amino groups. Tertiary
amino groups are preferred.
[0061] Complexing agents preferred for carrying out this invention
comprise ligands which are derived from compounds which have
primary amino groups and in which the H atoms on the amino group
are substituted by --CH.sub.2--COOH groups. Examples comprise
ethylenediaminetetraacetic acid (EDTA),
diethylenetriaminepentaacetic acid (DTPA),
hydroxyethylethylenediaminetriacetic acid (HEDTA), nitrilotriacetic
acid (NTA) or rnethylglycinediacetic acid (MGDA).
Ethylenediaminetetraacetic acid and methylglycinediacetic acid are
preferably used for carrying out the present invention, and
methylglycinediacetic acid is very particularly preferred. The
complexing agent can be used in the form of acids or in the form of
salts.
[0062] The complexing agents may also be polymeric complexing
agents. Suitable polymeric complexing agents are in particular
those which are derived from polymers which have primary and/or
secondary amino groups and in which some or all of the H atoms on
the amino groups have been substituted by --CH.sub.2--COOH groups.
Preferred polymeric complexing agents are polyethyleneimines
modified with --CH.sub.2--COOH groups. As a rule, at least 50%,
preferably at least 60%, particularly preferably at least 75%, of
the H atoms on the amino groups should be substituted. The
preparation of such polymeric complexing agents is described in WO
2004/001099.
[0063] The person skilled in the art in the area of water-soluble
complexing agents knows that the solubility of COOH-containing
complexing agents in water may be dependent on the pH. The pH
chosen for the respective intended use should therefore be selected
as a reference point in each case. A complexing agent which has
insufficient solubility for the intended use at a certain pH may
have a sufficient solubility at another pH.
[0064] If present, the complexing agent is as a rule used in an
amount of from 0.01 to 10% by weight. From 0.1 to 10% by weight are
preferably used, particularly preferably from 0.1 to 5% by
weight.
[0065] The weight ratio of complexing agent to pickling inhibitor
is as a rule from 100:1 to 1:100, preferably from 50:1 to 1:50,
particularly preferably from 5:1 to 1:10. Depending on the acid
concentration, the following amounts have proven particularly
appropriate for use at room temperature. TABLE-US-00002 Amount of
acid [% by Pickling inhibitor [% Complexing agent weight] by
weight] [% by weight] 5 0.01-0.05 0.01-0.05 10 0.01-0.1 0.01-0.5 15
0.05-0.2 0.01-1 20 0.1-0.25 0.01-1
[0066] The pH of the composition is determined by a person skilled
in the art according to the intended use. It can be established by
the type and amount of the acid and, if appropriate, further
components, depending on the intended use. Suitable buffer systems,
e.g. phosphate buffer or citrate buffer, can also be used for
stabilizing the pH. As a rule, the pH is from 0 to less than 7,
preferably from 6.5 to 2, particularly preferably from 3 to 6.
[0067] The formulation which comprises [0068] (a) from 60 to 99.97%
by weight of a mixture of water and at least one acid, [0069] (b)
from 0.01 to 2% by weight of at least one of said alkyne
alkoxylates, [0070] (c) from 0.01 to 20% by weight of at least one
surface-active substance and [0071] (d) from 0.01 to 10% by weight
of at least one of said chelate-forming complexing agents is
particularly preferred for carrying out the novel process.
[0072] Very particularly preferably, the amounts are: (a) from 70
to 98.9% by weight, (b) from 0.1 to 2% by weight, (c) from 0.5 to
15% by weight, and (d) from 0.5 to 10% by weight.
[0073] In a further preferred embodiment of the invention, the
pickling inhibitors used according to the invention are used
together with water-soluble cationic, nitrogen-containing polymers
(V) which comprise quaternized ammonium groups ##STR2##
[0074] R.sup.5 and R.sup.5' being identical or different and being
saturated or unsaturated, substituted or unsubstituted aliphatic
radical, saturated or unsaturated, substituted or unsubstituted
alicyclic radical or substituted or unsubstituted araliphatic
radical. The groups A linking the ammonium groups are hydrocarbon
groups, in particular alkylene groups in which further functional
groups and/or heteroatoms may also be incorporated. For example,
nonneighboring groups can be replaced by O atoms or N atoms.
Suitable functional groups are in particular urea groups
--NC--CO--NH--. X is chosen by a person skilled in the art
according to the desired properties. Particularly suitable polymers
usually have a molecular weight of 1000-100,000, preferably
1500-50,000, particularly preferably 2000-20,000 g/mol.
[0075] The cationic polymer V is preferably one which comprises two
different linking groups A' and A''. ##STR3##
[0076] As shown, the radicals A' and A'' can preferably be arranged
so that they are alternating, but they can also in principle occur
in any desired sequence and number in the polymer.
[0077] The group A' is a group which comprises alkylene units and
urea units: ##STR4## here, k and k', independently of one another,
are each a natural number from 1 to 5, preferably 2 or 3. R.sup.6
and R.sup.6', independently of one another, are H or a
straight-chain or branched alkyl radical of 1 to 12 carbon atoms.
R.sup.6 and R.sup.6' are preferably selected from the group
consisting of H, --CH.sub.3 and --C.sub.2H.sub.5, and R.sup.6 and
R.sup.6' are particularly preferably H.
[0078] The group A'' is a straight-chain or branched alkylene group
of 2-20 carbon atoms. The group may be substituted by groups such
as --OH or .dbd.O. Furthermore, non-neighboring, nonterminal carbon
atoms may also be substituted by one or more identical or different
heteroatoms, such as O, S and/or N. O-substituted radicals are
preferred.
[0079] A'' is preferably a radical of the formula
--CH.sub.2CH.sub.2--(OCH.sub.2CH.sub.2).sub.1--, where 1 is a
natural number from 1 to 3. A'' is particularly preferably
--CH.sub.2CH.sub.2--O--CH.sub.2--CH.sub.2--.
[0080] Such cationic polymers, their preparation and properties are
known in principle, in particular as cosmetic hair compositions.
For example, reference may be made to DE-A 25 21 960 or DE-A 2 924
230.
[0081] It is particularly preferably a polymer of the formula VI:
##STR5##
[0082] The cationic polymers are preferably used in the same
amounts as the complexing agents. Of course, both complexing agents
and cationic polymers may also be used together with the pickling
inhibitor.
[0083] The formulation used may also comprise further components or
assistants, depending on the intended use.
[0084] In order to improve the removal of greases in the degreasing
by pickling, it may be advantageous to add small amounts of
water-miscible organic solvents to the composition. The amount of
optionally added organic solvents is, as a rule, from 0 to 10% by
weight. Examples of suitable, water-miscible solvents comprise
monoalcohols, such as methanol, ethanol or propanol, higher
alcohols, such as ethylene glycol or polyetherpolyols, and ether
alcohols, such as butyl glycol or methoxypropanol.
[0085] Examples of further assistants comprise, for example,
antifoams, such as polypropoxylates or silicone ethers. The type
and amount of additional components or assistants are determined by
a person skilled in the art according to the intended use. The
amount of optionally added further assistants is as a rule from 0
to 5% by weight.
[0086] In addition to the abovementioned components, formulations
for phosphating comprise zinc ions, phosphate ions and, if
appropriate, further components, such as fluoride in particular
complex fluorides, accelerators, such as nitrite ions or further
metal ions, such as manganese, copper, magnesium or nickel ions.
Acidic formulations for phosphating are disclosed, for example, in
WO 99/32687, DE-A 199 23 084 or DE-A 197 23 084.
[0087] In the novel process, the metallic surface is brought into
contact with the aqueous formulation, for example by spraying,
dipping or rolling on. After a dipping process, the workpiece can
be allowed to drip to remove excess treatment solution; however, in
the case of metal sheets, metal foils or the like, excess treatment
solutions can, for example, also be squeezed out.
[0088] It is of course also possible to treat metallic surfaces in
the interior of plants. Internal deposits in boilers, pipelines or
the like can be removed by filling the plant with the formulation
used according to the invention or flushing it therewith. The
dissolution of the deposit can be accelerated by circulating the
formulation in the plant by pumping.
[0089] The novel process can optionally also comprise one or more
pretreatment steps. For example, the metallic surface can be
cleaned prior to pickling with the formulation used according to
the invention, for example to remove greases or oils. This is
especially advisable in particular in the case of phosphating.
[0090] Furthermore, the process may optionally comprise after
treatment steps. Examples of these are in particular washing steps
in which the treated surface is washed with suitable cleaning
liquids, in particular water, in order to remove, for example,
residues of the formulation used according to the invention from
the surface.
[0091] It is also possible to employ no-rinse processes in which
the treatment solution is dried in immediately after application,
without washing off, directly in a drying oven.
[0092] The treatment can be carried out batchwise or continuously.
A continuous process is particularly suitable for treating strip
metals. Here, the metal strip is passed through a tank or a spray
apparatus and optionally through further pretreatment or after
treatment stations.
[0093] Temperature and duration of the treatment are determined by
a person skilled in the art according to the intended use. A higher
temperature accelerates on the one hand the pickling attack on
layers to be removed but, on the other hand, also the pickling
attack on the metal itself. In general, the temperature of the
treatment is from 20 to 80.degree. C., without there being any
intention thereby to limit the invention to this range. The
duration of treatment may be from 1 second to several hours.
Usually, the duration of treatment is shorter at higher
temperatures than at lower temperatures.
[0094] In the pickling of steel strips, a temperature of from 60 to
80.degree. C., for example 70.degree. C., in combination with
contact times of from 1 to 10 seconds has proven particularly
useful. For steel strips, pickles containing sulfuric or
hydrochloric acid are particularly suitable.
[0095] In the novel process, the pickling attack on the metal is
inhibited substantially more strongly than with the use of
unalkoxylated pickling inhibitors. Complexing agents have a
synergistic effect together with the alkoxylated pickling
inhibitors and substantially reduce the pickling attack
further.
[0096] In a further preferred embodiment of the invention, the
acidic, aqueous composition can be used as a fountain solution for
offsetting. The ethoxylated alkynols present in the formulation
advantageously prevent undesired corrosion on printing press and
printing plates. Suitable acids for this application are in
particular phosphoric acid or organic acids, such as, for example,
succinic acid, usually as components of a buffer system.
[0097] The conventional additives known to a person skilled in the
art can be used as further components for this application.
Examples comprise alcohols, such as glycerol, hydrophilic polymers,
such as gum arabic or cellulose derivatives, surface-active
substances and biocides.
[0098] The examples which follow illustrate the invention:
Abbreviations Used:
[0099] PA: Propargyl alcohol [0100] BDA: 2-Butyne-1,4-diol [0101]
EO: Ethylene oxide [0102] PO: Propylene oxide [0103] PA-n EO:
Propargyl alcohol ethoxylated with on average n ethylene oxide
units [0104] PA-n PO: Propargyl alcohol propoxylated with on
average n propylene oxide units [0105] BDA-n EO: 2-Butyne-1,4-diol
ethoxylated with on average n ethylene oxide units [0106] BDA-n PO:
2-Butyne-1,4-diol propoxylated with on average n propylene oxide
units Preparation of The Pickling Inhibitors:
[0107] The preparation of the alkoxylated used for the novel
process was effected on the basis of the method disclosed in DE-A
22 41 155.
[0108] The preparation of an ethylene oxide adduct starting from
propargyl alcohol is described below by way of example.
[0109] Ethoxylated propargyl alcohol (PA-2 EO)
[0110] In a 6 l pressure-resistant reactor having an anchor
stirrer, temperature control and nitrogen inlet, 1200 g of
propargyl alcohol are reacted with 24 g of triphenylphosphine and
with 2 equivalents of ethylene oxide or propylene oxide in the
course of 12 hours under a nitrogen atmosphere at 55-65.degree.
C.
Formulations Used:
[0111] The following solutions were used for the examples:
Cleaning Agents
Solutions 1 to 3
[0112] In each case solutions of corrosion inhibitor (if present)
and complexing agent (if present) in water were prepared. The
amounts of corrosion inhibitor and complexing agent are shown in
each case in tables 1 to 4. The pH was established in each case
with an acid. The total amount was in each case 100 g.
TABLE-US-00003 Solution 1 brought to pH 3.5 with 15% strength HCl
Solution 2 brought to pH 1 with concentrated H.sub.2SO.sub.4
Solution 3 brought to pH 3.5 with concentrated H.sub.3PO.sub.4
[0113] TABLE-US-00004 Pickling degreasers Solution 4 1 g pickling
inhibitor (according to table 5) 3 g nonionic surfactant: saturated
C.sub.13-oxo alcohol, ethoxylated, on average 8 EO units 0.2 g
anionic surfactant: acidic phosphoric ester of a fatty alcohol
alkoxylate 50 g conc. HCl. (37% HCl) 45.8 g water Water content:
77.3% Content of 95.8% water + acid: Solution 4a as for solution 4,
additionally 0.2% by weight of methylglycinediacetic acid (0.2% by
weight of water less) Solution 5 1 g pickling inhibitor (according
to table 5) 3 g nonionic surfactant: saturated C.sub.13-oxo
alcohol, ethoxylated, on average 8 EO units 3 g
3-nitrobenzenesulfonic acid 0.5 g alkylphenol ether sulfate, Na
salt, 40% strength 50 g conc. HCl (37% HCl) 42.5 g water Water
content: 74.3% Content of 92.8% water + acid: Solution 6 2 g
pickling inhibitor (according to table 5) 0.5 g nonionic
surfactant: oleylamine, ethoxylated, on average 12 EO units 0.5 g
nonionic surfactant: saturated C.sub.13-oxo alcohol, ethoxylated,
on average 8 EO units 25 g conc. H.sub.2SO.sub.4 (96%) 72 g water
Water content: 73% Content of 97% water + acid:
[0114] TABLE-US-00005 Acidic rust remover Solution 7 1 g pickling
inhibitor (according to table 5) 12 g nonionic surfactant:
saturated C.sub.13-15-oxo alcohol, ethoxylated, on average 8 EO
units 5 g dodecylbenzenesulfonic acid 40 g conc. H.sub.3PO.sub.4
(85%) 42 g water Water content: 48% Content of 82% water + acid:
Solution 7a as for solution 7, additionally 0.2% by weight of
methylglycinediacetic acid (0.2% by weight of water less)
[0115] TABLE-US-00006 Acidic cleaning agents Solution 8 5 g
pickling inhibitor (according to table 5) 8 g nonionic surfactant:
saturated C.sub.13-oxo alcohol, ethoxylated, on average 12 EO units
50 g conc. H.sub.3PO.sub.4 (85%) 37 g water Water content: 44.5%
Content of water + 87% acid:
[0116] Polymeric complexing agents and cationic polymers as
additives.
[0117] In each case 0.5% strength solutions of corrosion inhibitor
(if present) and 0.25% strength solution of complexing agent (if
present) in water were prepared. The total amount was in each case
100 g. TABLE-US-00007 ##STR6## Solution 9 0.5 g of pickling
inhibitor, brought to pH 1 with concentrated H.sub.2SO.sub.4 and
dissolved with 50 g/l Fe(II) sulfate. Solution 10 As for solution
9, additionally 0.25% by weight of methylglycine- diacetic acid
Solution 11 As for solution 9, additionally 0.25% by weight of a
polymeric complexing agent (polyathyleneimine, modified with acetic
acid groups, Na salt) Solution 12 As for solution 9, additionally
0.25% by weight of a cationic polymer of the formula
General Experimental Method: [0118] 1. Measurement principle:
[0119] Defined test sheets of St 1.0037, Al 99.9 or Zn 99.8 are
each dipped into a constant test solution (see solutions 1-7) for 1
hour or 24 hours at room temperature, and the mass loss per unit
area is determined gravimetrically by means of differential
weighing. [0120] The preparation and cleaning of the metal sheets
are effected according to ISO 8407 in a material-specific manner
and is mentioned explicitly here for St 1.0037. [0121] 2.
Preparation of the metal sheets: [0122] Degreasing: In a plastic
tank having two sheet-like electrodes (stainless steel or graphite)
which are larger than the test sheet, a solution of the degreasing
bath of the following composition is used: [0123] 20 g of NaOH
[0124] 22 g of Na.sub.2CO.sub.3 [0125] 16 g of
Na.sub.3PO.sub.4.12H.sub.2O [0126] 1 g of
ethylenediaminetetraacetic acid (EDTA) [0127] 0.5 g of nonionic
surfactant: alkylphenol, ethoxylated, on average [0128] 10 EO units
in about 940 ml of demineralized water [0129] NaOH,
Na.sub.2CO.sub.3 and Na.sub.3PO.sub.4 are dissolved in succession
in demineralized water with stirring. At the same time, EDTA and
the surfactant are predissolved separately in demineralized water,
this being effected in the case of the surfactant solution at a
temperature of 50.degree. C. The solutions of EDTA and surfactant
are then added to the sodium hydroxide solution in a measuring
cylinder and, after cooling, are made up to 1000 ml with
demineralized water. [0130] Rust removal: In a plastic tank having
two sheet-like electrodes which are larger than the test sheet, a
solution of the rust removal bath of the following composition is
used: 100 g of diammonium citrate in 1000 ml of water with
demineralized water. [0131] A steel sheet measuring 50 mm.times.20
mm.times.1 mm is wiped with a paper cloth and dipped into the
degreasing bath between the electrodes at 10 volt and is connected
as the cathode. The voltage is adjusted so that the current is 1 A.
After ten seconds, the steel sheet is removed and is washed with
running water for five seconds. [0132] The steel sheet is dipped
into the rust removal bath between the electrodes at 10 V and is
connected as the cathode. The voltage is adjusted so that the
current is 1 A. After three minutes, the steel sheet is removed and
is washed with running demineralized water for five seconds, blown
off with air and used directly for the test. [0133] 3. Pickling
tests [0134] The metal sheet measuring 50 mm.times.20 mm.times.1 mm
is electrolytically degreased and derusted. [0135] The initial mass
is determined by means of an analytical balance. The metal sheet is
used directly after the weighing. The prepared metal sheet is
placed obliquely in a 200 ml glass bottle containing test solution.
The angle between steel sheet and base is 35.degree.. The glass
bottle is closed firmly and stored at room temperature. During the
storage, the glass bottle is shaken once briefly every 6 hours.
[0136] The metal sheet is removed from the solution, washed with
demineralized water, brushed off with steel wool, washed with
demineralized water and blown dry with air. The mass is then
determined. [0137] The gravimetric pickling test is carried out as
a ten-fold determination and the mean value is calculated. [0138]
Simultaneously with the test, a ten-fold determination without
pickling inhibitor and with but-2-yne-1,4-diol or propargyl alcohol
as pickling inhibitor is carried out. [0139] 4. Evaluation of the
results [0140] For each metal sheet, the difference between first
and second weighing in mg/cm.sup.2 is noted (.DELTA.m.sub.Sample).
In addition, the efficiency E of the active substance, whereby the
mass loss .DELTA.m.sub.Sample is expressed in relation to the mass
loss in the corrosion test without inhibitor, .DELTA.m.sub.0, can
be specified. The following is applicable:
E=(.DELTA.m.sub.0-.DELTA.m.sub.Sample)/.DELTA.m.sub.0
[0141] Accordingly, a maximum inhibition efficiency may be 1 (no
removal of metal, or 0 (in demineralized water), but may also be
<0 if the introduction of an additive leads to accelerated
corrosion.
EXAMPLES
Tests Without Complexing Agent
Examples 1 to 8, Comparative Examples 1 to 3
[0142] Solution 1 was used for the experiments (HCl, pH 3.5). The
metal removal per unit area at 30.degree. C. after 1 hour and 24
hours and the inhibition efficiency E were determined for sheets of
steel 1.0037 according to the method described generally above. The
pickling inhibitors shown in table 1 were used in the amounts
shown. A complexing agent was not present in these experiments. The
results are summarized in table 1.
Examples 9 and 10, Comparative Examples 4 and 5
[0143] Solution 2 was used for the experiments (H.sub.2SO.sub.4, pH
1). The metal removal per unit area at 30.degree. C. after 1 hour
and 24 hours and the inhibition efficiency E were determined for
sheets of steel 1.0037 according to the method described generally
above. The pickling inhibitors shown in table 2 were used in the
amounts shown. A complexing agent was not present in these
experiments. The results are summarized in table 2.
Synergistic Mixture With Complexing Agent
Examples 11 to 18, Comparative Examples 6 and 7
[0144] Solution 1 was used for the experiments (HCl, pH 3.5). The
inhibition efficiency E was determined for sheets of steel 1.0037
according to the method described generally above at room
temperature after 1 hour. The pickling inhibitors and complexing
agents shown in table 3 were used in the amounts shown. The results
are summarized in table 3.
Examples 19 to 30, Comparative Examples 8 to 10
[0145] Solution 3 was used for the experiments (HCl, pH 3.5). The
inhibition efficiency E was determined for sheets of steel 1.0037
according to the method described generally above at room
temperature after 1 hour. The pickling inhibitors and complexing
agents shown in table 4 were used in the amounts shown. The results
are summarized in table 4.
Examples 31 to 42, Comparative Examples 11 to 15
[0146] The solutions 4 to 8 were used for the experiments (see
above). The inhibition efficiency E was determined for sheets of
steel 1.0037 according to the method described generally above at
room temperature after 1 hour. The pickling inhibitors and
complexing agents shown in table 5 were used in the amounts shown.
The results are summarized in table 5. TABLE-US-00008 TABLE 1 Test
with solution 1 (HCl, pH 3.5) Metal removal at 30.degree. C. [mg]
Inhibition efficiency E No. Pickling inhibitor Amount [% by wt.]
After 1 h After 24 h [%] after 1 h Comparative example 1 -- -- 60
>80 0 Comparative example 2 BDA 5 10 42 83 Example 1 BDA-2 EO 5
8 35 86 Example 2 BDA-2 PO 5 7 33 88 Comparative example 3 PA 5 16
68 73 Example 4 PA-2 PO 0.5 12 55 80 Example 5 PA-2 PO 1 8 25 86
Example 6 PA-2 PO 5 2 16 97 Example 7 PA-7 EO 5 14 65 77 Example 8
PA-2 EO 5 3 18 95
[0147] TABLE-US-00009 TABLE 2 Tests with solution 2
(H.sub.2SO.sub.4, pH 1) Metal removal at 30.degree. C. [mg]
Inhibition efficiency E No. Pickling inhibitor Amount [% by wt.]
After 1 h After 24 h [%] after 1 h Comparative example 4 -- -- 1.2
>5 0 Comparative example 5 BDA 2 0.4 1.5 67 Example 9 BDA-2 EO 1
0.3 1.2 75 Example 10 BDA-2 PO 1 0.2 0.9 83
[0148] TABLE-US-00010 TABLE 3 Tests with solution 1 (HCl, pH 3.5)
Pickling inhibitor Complexing agent Inhibition efficiency E No.
Type Amount [% by wt.] Type Amount [% by wt.] [%] after 1 h
Comparative example 6 -- -- Nitrilotriacetic acid 1 -60 Example 11
PA-2 PO 0.5 -- -- 44 Example 12 PA-2 PO 0.5 Nitrilotriacetic acid 1
70 Example 13 PA-2 EO 0.5 -- -- 8 Example 14 PA-2 EO 0.5
Nitrilotriacetic acid 1 50 Comparative example 7 -- -- EDTA 1 -40
Example 15 PA-2 PO 0.5 -- -- 44 Example 16 PA-2 PO 0.5 EDTA 1 70
Example 17 PA-2 EO 0.5 -- -- 8 Example 18 PA-2 EO 0.5 EDTA 1 70
[0149] TABLE-US-00011 TABLE 4 Tests with solution 3
(H.sub.3PO.sub.4, pH 3.5) Pickling inhibitor Complexing agent
Amount Amount Inhibition efficiency E No. Type [% by wt.] Type [%
by wt.] [%] after 1 h Comparative example 8 -- --
Methylglycinediacetic acid 1 -35 Example 19 PA-2 PO 0.5 -- -- 44
Example 20 PA-2 PO 0.5 Methylglycinediacetic acid 1 71 Example 21
PA-2 EO 0.5 -- -- 8 Example 22 PA-2 EO 0.5 Methylglycinediacetic
acid 1 35 Comparative example 9 -- -- Nitrilotriacetic acid 1 -16
Example 23 PA-2 PO 0.5 -- -- 44 Example 24 PA-2 PO 0.5
Nitrilotriacetic acid 1 71 Example 25 PA-2 EO 0.5 -- -- 8 Example
26 PA-2 EO 0.5 Nitrilotriacetic acid 1 29 Comparative example 10 --
-- EDTA 1 -27 Example 27 PA-2 PO 0.5 -- -- 44 Example 28 PA-2 PO
0.5 EDTA 1 48 Example 29 PA-2 EO 0.5 -- -- 8 Example 30 PA-2 EO 0.5
EDTA 1 48
[0150] TABLE-US-00012 TABLE 5 Testing of different cleaning,
pickling or deliming formulations Complexing agent Metal removal
Example No. Solution No. Pickling inhibitor Type Amount [by wt.] at
30.degree. C. [mg] Comparative example 11 4 BDA 0.015 Example 31 4
PA-2 PO -- -- 0.005 Example 32 4a PA-2 PO Methylglycinediacetic
acid 0.2 0.003 Example 33 4 PA-2 EO -- -- 0.012 Comparative example
12 5 BDA -- -- 0.480 Example 34 5 PA-2 PO -- -- 0.068 Example 35 5
PA-2 EO -- -- 0.195 Comparative example 13 6 BDA -- -- 0.105
Example 36 6 PA-2 PO -- -- 0.010 Example 37 6 PA-2 EO -- -- 0.090
Comparative example 14 7 BDA -- -- 0.015 Example 38 7 PA-2 PO -- --
0.090 Example 39 7a PA-2 PO Methylglycinediacetic acid 0.2 0.075
Example 40 7 PA-2 EO 0.110 Comparative example 15 8 BDA -- -- 1.710
Example 41 8 PA-2 PO -- -- 0.613 Example 42 8 PA-2 EO -- --
0.620
[0151] TABLE-US-00013 TABLE 6 Test with solution 9
(H.sub.2SO.sub.4, pH 1), comparison of different additives Metal
removal at 50.degree. C. Pickling inhibitor Amount of additive
Duration of action Inhibition efficiency PA-2-PO Type of additive
[% by weight 15 min E [%] Comparative example 16 0.5 -- -- 0.03 96
Comparative example 17 -- Cationic polymer 0.5 0.045 80 Example 43
0.5 Cationic polymer 0.5 0.011 >99 Example 44 0.5 Polymeric
complexing 0.25 0.010 >99 agent
[0152] The examples show that the alkoxylated pickling inhibitors
used according to the invention effect considerable better
inhibition than propargyl alcohol or butynediol. Thus, not only was
a substitute which is safer from the economical point of view
provided, but even a substitute having a better action. This
applies in particular to steel surfaces.
[0153] Moreover, they surprisingly cooperate in a synergistic
manner with complexing agents. Whereas the complexing agent when
used alone even accelerates the dissolution of the metal, the
combination of complexing agent and pickling inhibitor results in
even greater inhibition than with the pickling inhibitor alone.
* * * * *