U.S. patent application number 10/232816 was filed with the patent office on 2003-03-13 for wire based on zinc and aluminum and its use in thermal spraying for corrosion protection.
This patent application is currently assigned to Grillo-Werke AG. Invention is credited to Spriestersbach, Jochen, Staubwasser, Peter.
Application Number | 20030049157 10/232816 |
Document ID | / |
Family ID | 24632971 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030049157 |
Kind Code |
A1 |
Spriestersbach, Jochen ; et
al. |
March 13, 2003 |
Wire based on zinc and aluminum and its use in thermal spraying for
corrosion protection
Abstract
The wire based on zinc and aluminum contains from 8 to 33% by
weight of aluminum and up to 500 ppm of indium, in addition to zinc
and the usual impurities. This wire is suitable for thermal
spraying for corrosion protection, especially corrosion protection
against high atmospheric humidity and high chloride ion
concentrations according to DIN 50021-ss.
Inventors: |
Spriestersbach, Jochen;
(Marl, DE) ; Staubwasser, Peter; (Ratingen,
DE) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
Grillo-Werke AG
Duisburg
DE
|
Family ID: |
24632971 |
Appl. No.: |
10/232816 |
Filed: |
September 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10232816 |
Sep 3, 2002 |
|
|
|
09656423 |
Sep 6, 2000 |
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Current U.S.
Class: |
420/514 ;
148/441 |
Current CPC
Class: |
Y10T 428/12771 20150115;
C22C 18/04 20130101 |
Class at
Publication: |
420/514 ;
148/441 |
International
Class: |
C22C 018/00 |
Claims
1. A wire based on zinc and aluminum, characterized by containing
from 8 to 33% by weight of aluminum and up to 500 ppm of indium, in
addition to zinc and the usual impurities.
2. The wire according to claim 1, characterized by containing from
10 to 24% by weight of aluminum and from 10 to 300 ppm of
indium.
3. The wire according to claim 1 or 2, characterized by containing
less than 0.1% by weight of copper, less than 0.1% by weight of
iron and less than 1% by weight of lead.
4. Use of a wire according to any of claims 1 to 3 in thermal
spraying for corrosion protection.
5. The use according to claim 4 for corrosion protection against
high atmospheric humidity and high chloride ion concentrations
according to DIN 50021.
Description
[0001] The present invention relates to a wire based on zinc and
aluminum which can be used in thermal spraying for corrosion
protection, especially for corrosion protection against high
atmospheric humidity and high chloride ion concentrations, e.g., in
marine environments, thawing salt etc.
[0002] DE 30 07 850 C2 describes the use of a zinc alloy as a
powder for mechanical cladding, wherein an alloy of zinc and one or
more alloying additions is to be used, such as from 0.1 to 60% of
aluminum, up to 5% of nickel, up to 3% of magnesium, up to 3% of
copper, up to 2% of silicon, up to 1.5% of titanium, up to 1% of
antimony, up to 1% of silver, up to 0.5% of chromium, 0.5% of
beryllium, up to 0.1% of calcium, up to 0.1% of cobalt, up to 0.1%
of sodium, up to 0.1% of potassium, 0.1% of indium, up to 0.05% of
lithium, 0.05% of strontium, respectively based on the total weight
of the alloy except the weight of contaminations. In mechanical
cladding with a metal powder, this powder is mechanically applied
to the substrate to form a layer of 10 .mu.m. Roll-bonded cladding,
also using aluminum powder, is described, for example, in
Aluminium-Taschenbuch, 13th edition, 1974, page 927, paragraphs 1
and 2.
[0003] Also in the method according to DE 30 07 850 C2, the parts
to be mechanically clad, after degreasing, are subjected to a
surface cleaning and conditioning and arc coating to form a coating
layer. The thus prepared coating layers are additionally subjected
to a chromate treatment. This method is fundamentally different
from thermal spraying using wires which are employed in wire flame
spraying or wire arc spraying. Wire flame spraying and wire arc
spraying can also be employed later for finished building
components or in situ for bridges, scaffolds, cranes etc. In
contrast, roll-bonded cladding cannot be performed later.
[0004] DD-PS 4 822 describes that it is possible to process
zinc-aluminum alloys in the range of eutectoid decay by annealing
followed by quenching to yield articles having a high plasticity.
From this material, a wire can be prepared by extruding from an
alloy of 80% zinc and 20% aluminum.
[0005] To date, wires for thermal spraying have consisted of either
high-purity zinc, an alloy of only zinc/aluminum with 15% by weight
of aluminum, or aluminum with 5% by weight of magnesium.
[0006] One drawback of thermally sprayed surfaces of high-purity
zinc or zinc with 15% by weight of aluminum is that they corrode
fast and more severely than aluminum with 5% magnesium under the
above mentioned conditions. Therefore, additional protective
measures, such as paint coats, are necessary for zinc and
zinc/aluminum coatings under moisture and chloride exposure.
[0007] In the condensed water test according to DIN 50018-KFW 0.2
s, a severe corrosion of high-purity zinc is observed while zinc
with 15% of aluminum exhibits a clearly more favorable
performance.
[0008] But also coatings of aluminum with 5% magnesium, which show
high stability towards high moisture contents and high chloride ion
levels, corrode more severely than zinc with 15% by weight of
aluminum in the condensed water test.
[0009] Thus, it has been the object of the invention to provide a
zinc wire based on zinc and aluminum which exhibits a high
corrosion resistance both in the condensed water test and in the
salt-spray test according to DIN 50021 and thus, if possible,
exhibits the same corrosion resistance as aluminum with 5%
magnesium, also against high atmospheric humidity and high chloride
ion levels, i.e., the salt-spray test according to DIN 50021, or
even a higher corrosion resistance.
[0010] This object has now been achieved by a wire based on zinc
and aluminum containing from 8 to 33% by weight of aluminum and up
to 500 ppm of indium, in addition to zinc and the usual impurities.
Preferably, the wire contains from 10 to 24% by weight of aluminum
and from 10 to 300 ppm of indium.
[0011] Even more preferably, the wire contains from 15 to 22% by
weight of aluminum and from 20 to 200 ppm of indium.
[0012] Among the numerous Examples of DE 30 07 850 C2 are three
Examples in which 0.1% indium was employed, namely Examples 41, 62
and 74. However, such a high amount of indium results in severe
brittleness and poor processibility of the wires. Therefore,
according to the invention, the amount of indium is limited to a
maximum of 500 ppm, and preferably, only from 10 to 300 ppm of
indium is used. A zinc-aluminum wire with 0.08% of indium already
becomes totally brittle in the condensed water test.
[0013] Further, from DE 30 07 850 C2, it can be seen that the
addition of 0.1% by weight of indium to a zinc powder with 5%
aluminum has not resulted in an optimum corrosion resistance by
far. Thus, it was surely not obvious to process an alloy comprising
less indium into a wire in order to obtain a material which has
optimum properties if processed from a wire into a corrosion
protection which can be applied later by wire flame spraying or arc
spraying.
[0014] Optimum results are achieved when the content of usual
impurities is kept as low as possible. In particular, as little as
possible copper, iron and lead should be contained in the
alloy.
[0015] In principle, all zinc grades according to EN 1179 can be
employed as a starting material for the wire, zinc grades Z1 to Z4
being preferred because they contain clearly less lead, iron and
copper than the maximum value desired according to the
invention.
[0016] As the alloy component aluminum, the grades according to EN
576 meeting the purity requirements demanded can be employed in
principle.
[0017] The wire according to the invention can be prepared by usual
methods, namely by casting the liquid alloy as a cast strand
followed by rolling and drawing. For these methods, alloys
comprising only from 10 to 24% by weight of aluminum are preferred,
on the other hand, since alloys having a higher aluminum content
are more difficult to process.
[0018] The wire according to the invention can be employed for
thermal spraying in the conventional way, for example, by wire
flame spraying or wire arc spraying. These methods are mainly
distinguished by different process temperatures and thus by
different coating efficiencies.
[0019] From the following Examples and Comparative Examples, it can
be seen that the novel wire has clearly improved properties, and
its overall properties are superior to those found in the whole
prior art.
EXAMPLE 1
[0020] From the accompanying FIG. 1, it can be seen that pure zinc
exhibits the poorest values in the condensed water test according
to DIN 50018-KFW 0.2 s, but aluminum with 5% by weight of magnesium
also exhibits severe corrosion. The conventional wire made of zinc
with 15% by weight of aluminum exhibits good values. By the
addition of 400 ppm of indium, its performance is neither improved
nor deteriorated. Zinc wires with 22%, 33% or 55% by weight of
aluminum already exhibit poorer values. Zinc alloys with more than
25% by weight of aluminum are increasingly difficult to process
into a wire.
EXAMPLE 2
[0021] The same wires as in Example 1 are subjected to the
salt-spray test according to DIN 50021-ss. The results are shown in
FIG. 2. It can be seen that pure zinc again provides the poorest
results and, in addition, shows formation of red rust. In contrast,
aluminum with 5% magnesium, which has been selected for such
conditions to date, shows clearly better values and no formation of
red rust.
[0022] In comparison, zinc with 15% aluminum has a substantially
lower corrosion resistance and exhibits formation of red rust. By
adding more aluminum to the zinc, namely 22%, 33% or 55%, although
the corrosion performance is clearly improved over that of only 15%
aluminum, formation of red rust is still observed. Only the
addition of 400 ppm of indium to a zinc/aluminum alloy with 15%
aluminum achieves results which are equivalent or even better than
those achieved with aluminum to which 5% magnesium is added.
Especially for short weathering times, this alloy is even superior
to aluminum with 5% magnesium.
EXAMPLE 3
[0023] Wires based on zinc and aluminum containing 22% by weight of
aluminum and increasing amounts of indium are subjected to a
salt-spray test according to DIN 50021-ss. The results are
summarized in FIG. 3, with high-purity zinc and zinc with 15%
aluminum again being included for comparison. It can be seen that
20 ppm of indium already results in a significant improvement of
the corrosion performance, and increasing amounts of indium can
further improve the corrosion performance. Amounts of over 500 ppm
of indium are neither reasonable in terms of cost, nor do they
result in a further improvement of properties. In addition, it is
to be noted that the addition of larger amounts of indium
deteriorates the processibility of the alloy into a wire.
EXAMPLE 4
[0024] Preliminary examinations with different purity grades of
zinc and aluminum revealed that impurities of more than 0.1% by
weight of copper and more than 0.1% by weight of iron, in
particular, result in deteriorated properties and especially
enhance intercrystalline corrosion, while more than 1% by weight of
lead results in deteriorated mechanical properties.
* * * * *