U.S. patent application number 14/272602 was filed with the patent office on 2014-11-20 for method for depositing an anticorrosive coating.
The applicant listed for this patent is Werner Krommer, Andreas Trautmann. Invention is credited to Werner Krommer, Andreas Trautmann.
Application Number | 20140342095 14/272602 |
Document ID | / |
Family ID | 51895987 |
Filed Date | 2014-11-20 |
United States Patent
Application |
20140342095 |
Kind Code |
A1 |
Krommer; Werner ; et
al. |
November 20, 2014 |
METHOD FOR DEPOSITING AN ANTICORROSIVE COATING
Abstract
A method for depositing an anticorrosive coating on components,
wherein an aluminum-zinc coating is used as an anticorrosive
coating, and wherein the anticorrosive coating is deposited by
thermal spraying, wherein an inert carrier gas with a reducing gas
component is used for the thermal spraying.
Inventors: |
Krommer; Werner; (Landshut,
DE) ; Trautmann; Andreas; (Munich, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Krommer; Werner
Trautmann; Andreas |
Landshut
Munich |
|
DE
DE |
|
|
Family ID: |
51895987 |
Appl. No.: |
14/272602 |
Filed: |
May 8, 2014 |
Current U.S.
Class: |
427/456 |
Current CPC
Class: |
C23C 4/131 20160101;
C23C 4/08 20130101 |
Class at
Publication: |
427/456 |
International
Class: |
C23C 4/08 20060101
C23C004/08; C23C 4/12 20060101 C23C004/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2013 |
DE |
102013008517.9 |
Jun 25, 2013 |
EP |
13003229.5 |
Jul 30, 2013 |
DE |
102013012662.2 |
Claims
1. A method for depositing an anticorrosive coating on components,
wherein an aluminium-zinc coating is used at least as a component
part of an anticorrosive coating, characterised in that the
aluminium-zinc coating is deposited by thermal spraying, wherein an
inert gas with a reducing gas component is used for the thermal
spraying.
2. The method according to claim 1, wherein a further coating is
deposited on or under the aluminium-zinc layer.
3. The method according to claim 2, wherein the further coating
comprises one or more coloured layers.
4. The method according to claim 1, wherein hydrogen is used as the
reducing gas component.
5. The method according to claim 1, wherein nitrogen is used as the
inert gas.
6. The method according to claim 1, wherein a hydrogen-nitrogen
mixture is used for the thermal spraying.
7. The method according so claim 1, wherein arc spraying is used
for the thermal spraying.
8. The method according to claim 1, wherein the aluminium-zinc
coating layer alone or as a component part of an anticorrosive
coating is deposited on areas subject to high mechanical load to
reduce wear and corrosion.
9. The method according to claim 1, wherein a proportion of the
reducing gas component in the inert gas amounts to between 0.1% and
10%
10. The method according to claim 1, wherein a proportion of the
reducing gas component in the inert gas amounts to between 2% and
4%.
11. The method according to claim 1, wherein a thickness of the
aluminium-zinc coating amounts to between 50 .mu.m and 150
.mu.m.
12. The method according to claim 1, wherein a thickness of the
aluminum-zinc coating amounts to between 75 .mu.m and 120
.mu.m.
13. The method according to claim 1, wherein a thickness of the
aluminium-zinc coating amounts to 100 .mu.m.
14. The method according to claim 1, wherein the adhesiveness of
the spray-metallised aluminium-zinc layer amounts on average to
between 7.0 and 8.0 MPa.
15. The method according to claim 2, wherein the adhesiveness of
the further layers to the spray-metallised aluminium-zinc layer
itself or of the anticorrosive coating to the coated, material
amounts on average to between 7.0 and 8.0 MPa.
16. The method according to claim 1, wherein the anticorrosive
coating is deposited on components that are exposed to a corrosive
atmosphere.
17. The method according to claim 1, wherein the corrosive
atmosphere is selected from the group consisting of a sea water
atmosphere, a marine atmosphere and a chemical atmosphere.
18. The method according to claim 1, wherein the anticorrosive
coating is deposited on components of a wind energy plant.
19. The method according to claim 1, wherein the wind energy plant
is an offshore wind energy plant.
20. The method according to claim 1, wherein the inert gas with the
reducing gas component is nitrogen and hydrogen.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from German Patent
Application Ser. No. DE 102013008 517.9 filed May 16, 2013,
European Patent Application Ser. No. EP 13003220.5 filed Jun. 25,
2013 and German Patent Application No. DE 102013012662.2 filed Jul.
30, 2013.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method for depositing an
anticorrosive coating on components, wherein the anticorrosive
coating is constituted at least in part as an aluminium-zinc
coating; a use of a gas mixture containing a reducing gas for
depositing an anticorrosive coating on components, as well as a use
of an aluminium-zinc coating as a component part of an
anticorrosive coating for components.
[0003] In a method for thermal spraying, spray particles are
directed onto a workplace with the aid of a carrier gas. The spray
particles form a coating on the workpiece. The spray particles
adhere on the workplace surface and to one another on account of
the kinetic energy and the heat, which they exhibit when they
strike the workpiece. Active corrosion protection by means of an
anticorrosive coating of aluminium and/or zinc is the largest area
of application of thermal spraying. Approximately 20,000 tonnes of
wire from these materials is processed each year, with an
increasing trend. The spraying application of both materials, also
in combination, is in part standard in the commercial, offshore
sector, for example. In the area of offshore wind energy plants,
there is the particular requirement to keep maintenance intervals
as long as possible, which can he achieved, amongst other things,
by the use of durable surface coatings. Spray metallisation has
hitherto been used on offshore wind energy plants essentially on
components subject to high mechanical load, cues as flanges,
frames, rivet holes, bolt holes and support surfaces, etc.
[0004] The use of a gas mixture for thermal spraying is known from.
EF 1 674 590 A1. The spray material, is fused in an arc in the
course of arc spraying and atomised in a carrier gas to form spray
particles. A gas mixture containing hydrogen is used as a carrier
gas. For example, the gas mixture contains 1 to 30% by volume of
hydrogen.
[0005] For this invention, hydrogen is used as a pure carrier-gas
in order to bind atmospheric oxygen.
[0006] EP 2 186 593 A1 discloses a gas mixture, comprising a
mixture of argon, helium nitrogen, carbon dioxide or hydrogen or
mixtures thereof with a hydrocarbon gaseous under normal
conditions. The gas mixture is used, amongst other things, for
thermal, spraying and/or surface treatment by means of an arc. In
this invention, the mixtures are used in each case as a pure
carrier gas.
[0007] A problem of thermal spraying, however, is the influence of
oxygen on the spray material. On account of the high temperatures,
the spray material becomes highly oxidised in the presence of
oxygen. Oxygen can get to the spray material either through the
carrier gas, for which compressed air is often used, or through the
ambient air being swirled round with the carrier gas. Depending on
the available energy, the fused and atomised spray particles
combust completely or the metal particles oxidise to form, metal
oxides. The completely combusted spray particles are no longer
available tor the coating, when one speaks of erosion. The erosion
consequently reduces the efficiency of the deposition of the spray
material onto the workpiece. Efficiency is defined as the ratio
between the spray material forming the coating and the spray
material fused as a whole. The metal oxides, on the other hand,
arrive together with the metallic spray particles at the workpiece
and there become a component of the coating.
[0008] In the case of anticorrosive coatings, however, these metal
oxides lead to an impairment of the resistance of the coating in
the presence of corrosive ambient conditions. In order to prevent
this impairment of the qualify of the anticorrosive coating,
nitrogen can be used as a carrier gas. Nitrogen reduces the
oxidation of the spray particles. However, the oxidation is
suppressed only to an insufficient extent by the use of nitrogen
and the coatings then often do not meet the requirements made in
respect of quality.
[0009] The problem underlying the invention is to deposit, an
anticorrosive coating on workpieces or components, wherein as high
a degree of efficiency as possible is to be enabled for the
deposition of the anticorrosive coating and oxidation of the
anticorrosive coating due to the process of depositing the
anticorrosive coating is to be prevented.
SUMMARY OF THE INVENTION
[0010] This problem is solved by a method tor depositing an
anticorrosive coating on components, a use of a gas mixture
containing a reducing gas for depositing an anticorrosive coating
on components, as well as a use of an aluminium-zinc coating as a
component part of an anticorrosive coating for components.
Advantageous embodiments emerge from the sub-claims and the
following description.
[0011] In one embodiment of the invention, there is disclosed a
method for depositing an anticorrosive coating on components,
wherein an aluminium-zinc coating is used at least as a component
part of an anticorrosive coating, characterised in that the
aluminium-zinc coating is deposited by thermal spraying, wherein an
inert gas with, a reducing gas component is used for the thermal
spraying.
[0012] An aluminium-zinc coating is used at least as a component
part, of an anticorrosive coating for a method according to the
invention. This component part of the anticorrosive coating is
deposited on the components by means of thermal spraying, wherein
an inert carrier gas with a reducing gas component is used for the
thermal spraying. This coating is also referred to in the following
as a "spray-metallised coating".
[0013] The terra "components" is understood to mean both individual
components as component parts of larger installations or machines,
as well as workplaces which are not yet installed in installations
or machines and are coated according to the invention in the course
of their production process.
[0014] The corrosion protection effect of various anticorrosive
coatings that were deposited on components using different methods
was investigated within the scope of the invention. Aluminium-zinc
coatings and aluminium coatings were in each case deposited on
components in different layer thicknesses and forms using different
methods and were sealed on a case-by-case basis and provided with a
multilayer organic coating system. The main aim was to produce a
more oxide-free anticorrosive coating that is superior in its
effect to the layers oxidised by the process.
[0015] In the course of the invention, considerable advantages of
an aluminium-zinc coating as a component, part of an anticorrosive
coating that is deposited by thermal spraying were discovered,
wherein an inert carrier gas with, a reducing gas component is used
for the thermal spraying.
[0016] When a corrosive attack occurs, the aluminium-zinc coating
goes into solution and thus protects the underlying material of the
component, for example iron. The electrochemical potential of an
aluminium-zinc coating thermally sprayed with the reducing gas
component is higher than that of an aluminium-zinc coating that has
been thermally sprayed without, a reducing gas component, for
example under conventional air. The corrosion protection effect of
the aluminium-zinc coating thermally sprayed with the reducing gas
component is based on a combination of the cathodic protection of
the aluminium-rich phases, a selective corrosion of the zinc
combined with the formation of voluminous corrosion products
(aluminium hydroxides and zinc hydroxides). The latter become
deposited in the pores, which raises the density of the overcoat.
When a corrosive attack occurs, the aluminium atoms present in the
outermost molecular layer are oxidised first on account of their
affinity with oxygen which is double that of zinc. A zinc oxide
formation does not yet occur at this point. Aluminium oxides are
formed which are surrounded by zinc atoms. Once this has taken
place with all the aluminium atoms present in the first molecular
layer, zinc oxide is also formed, which is readily soluble and is
"flushed out" of the surface. An adherent, dense and very stable
aluminium oxide layer remains, which protects the underlying
aluminium-zinc coating. Moreover, a cathodic remote effect can be
achieved via gaps in the damaged aluminium-zinc coating.
[0017] A basic pre-requisite for the emergence of these properties,
which are decisive for the anticorrosive effect, is that the
deposited aluminium-zinc coating is not already completely
oxidised, by the process of the deposition and that the oxide is
able to form at the surface in order to achieve its full effect. In
the case of methods for the deposition of the aluminium-zinc
coating without a reducing gas component, for example with air,
each particle is already oxidised before it strikes the component.
Very pure aluminium-zinc coatings with little oxide content are
formed with aluminium-zinc coatings thermally sprayed, with the
reducing gas component.
[0018] The parameters of the thermal spraying primarily determine
the properties of the aluminium-zinc coating. The selection of the
nozzle system as well as parameters such as for example voltage,
current or the type of carrier gas influence the spray particles
when they are detached at electrodes and in their flight phase and
therefore the aluminium-zinc coating formed therefrom. Finely
atomised melt droplets at the same time signify a large specific
surface and therefore the promotion of the oxide content in the
aluminium-zinc coating. This oxidation can be reduced considerably
by the use of inert carrier gases with a reducing gas
component.
[0019] A second coating, in particular one or more coloured layers,
is advantageously deposited over the aluminium-zinc coating. A
corrosion protection system comprising at least two layers is thus
produced. The aluminium-zinc coating according to the invention
forms the first layer, a so-called primer. The second coating forms
the second layer. The resistance capacity of the corrosion
protection can be further increased by the combined action of the
first anticorrosive coating and the second coating. The
adhesiveness of the second coating is improved considerably by the
presence of the anticorrosive coating according to the invention,
on the one hand compared to a "second" coating without an
underlying anticorrosive coating and on the other hand compared to
an anticorrosive coating that has not been thermally sprayed with
the reducing gas component.
[0020] The first layer "heals" damage, for example cracks, by flow,
The second layer limits this flow of the first layer in order that
this "healing" can take place and. the loss of material from the
first layer due to flow is limited.
[0021] In the present invention, therefore, an anticorrosive
coating containing a spray-metallised, layer is deposited on
workpieces or components, which in particular is carried out in
process technical terms in such a way that further coloured layers
are/have been deposited on this spray-metallised anticorrosive
coating in downstream or upstream process steps, so that, as a
result of the combined action of the spray-metallised layer and the
further coloured layers, a high-quality corrosion protection
results for the workpieces or components coated in this way, said
corrosion protection also withstanding the most challenging
corrosive media and environmental conditions. The highest possible
degree of efficiency for the deposition is enabled by the invention
for the deposition of the spray-metallised layer and ozidation of
the anticorrosive coating due to the process of depositing the
anticorrosive coating is prevented according to the invention.
[0022] Hydrogen is preferably used as a reducing gas component.
Nitrogen is also advantageously used as a carrier gas. A
hydrogen-nitrogen mixture is particularly preferably used. The
proportion of the reducing gas component, in the gas mixture
preferably amounts to between 0.1% and 10%, in particular between
2% and 4%.
[0023] A use of the gas mixture containing hydrogen disclosed in EP
1 674 590 A1 from the same applicant is also conceivable. In this
regard, reference should be made expressly to this specification
with regard to the corresponding disclosure. In particular, such a
gas mixture, which contains 3 to 7% by volume of hydrogen, is
suitable for a method according to the invention. In this
invention, however, hydrogen only was used as a carrier gas in
order to bind atmospheric oxygen (e.g. from the ambient air).
[0024] A gas mixture according to EP 2 186 593 A1, also from the
same applicant, is also conceivable. In this regard, reference
should be made expressly to this specification with regard to the
corresponding disclosure. Such a gas mixture comprises a mixture of
argon. Helium, nitrogen, carbon dioxide or hydrogen or mixtures
thereof with a hydrocarbon gaseous under normal conditions. In
particular, this gas mixture contains metered quantities of NO
and/or NO.sub.2. In this invention, the mixtures are used in each
case as a pure carrier gas.
[0025] Arc spraying is preferably used for the thermal spraying, in
the case of arc spraying, two wires are fused in an arc and
atomised with the aid of a carrier gas to form spray particles and
then conveyed to the component. The electric arc burns between the
two wires, which are constituted as an anode and a cathode. Only
electrically conductive materials therefore come into question as
wires. The two wires can be made from the same or from different
materials. Instead of wires, use can also be made of two small
metallic tubes. The arc is usually generated between the two wires
ends by the application of a voltage with a contact ignition, said
wires ends being fed towards one another in the spray gun. Filler
wires can also be processed, as a result of which it is also
possible to deposit hard material-containing layers for protection
against wear, said layers containing for example oxides, nitrides,
carbides or borides. Up to 20 kg per hour for example can be
processed for an aluminium-zinc coating. Arc spraying has ideal
pre-requisites for the deposition of a metallic anticorrosive
coating. Easy handling, use of favourable materials (through the
use of wire), high deposition rate with high efficiency, as well as
the covering of large areas in a short time.
[0026] A thickness of the spray-metallised coating preferably
amounts to between 50 .mu.m and 150 .mu.m, in particular between 75
.mu.m and 120 .mu.m, more especially 100 .mu.m.
[0027] The adhesiveness of the spray-metallised aluminium-zinc
coating preferably amounts, on average, to between 7.0 and 8.0 MPa
and the adhesiveness of the further coloured layers to the
spray-metallised layer itself or of the anticorrosive coating to
the coated material also amounts, on average, to between 7.0 and
8.0 MPa.
[0028] The anticorrosive coating is preferably deposited on
components that are exposed to a sea water atmosphere (C5-M) or a
maritime atmosphere (lm2), e.g. or. drilling rigs or on coastal
installations, and/or on components that are exposed to other
corrosive chemical atmospheres (C5-1), e.g. in chemical plants. The
anticorrosive coating is also suitable for components that are
exposed to an extreme climate, in particular a tropical climate,
e.g. metallisations of propane bottles for a tropical climate.
[0029] In a particularly preferred embodiment of the invention, the
anticorrosive coating is deposited on components of a wind energy
plant, in particular an offshore wind energy plant. The
anticorrosive coating is particularly suitable for being deposited
on wind towers of wind energy plants or offshore wind energy
plants. The anticorrosive coating can be deposited according to the
invention particularly easily on components subject to high
mechanical load, such as flanges, frames and support surfaces.
Maintenance intervals can be kept as long as possible due to the
adhesiveness and the durability of the anticorrosive coating
deposited according to the invention.
[0030] Furthermore, the invention relates to a use of a gas mixture
containing a reducing gas component for depositing an anticorrosive
coating on components, as well as a use of an aluminium-zinc
coating as an anticorrosive ceasing for components. Embodiments of
these uses according to the invention emerge in an analogous manner
from the above description of the method according to the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention will now be explained farther with the aid of
the appended drawing. In the figures:
[0032] FIG. 1 shows a component without an anticorrosive
coating.
[0033] FIG. 2 shows a component with an aluminium-zinc coating,
which has been deposited with air as a carrier gas.
[0034] FIG. 3 shows a component with an aluminium-zinc coating with
a gas mixture containing an active gas component as a carrier gas,
said aluminium-zinc coating having been deposited by means of an
embodiment of a method according to the invention and
[0035] FIG. 4 shows a magnified detail of the component from FIG. 3
to illustrate the effect, of the aluminium-zinc coating deposited
by means of an embodiment of a method according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] FIGS. 1 to 4 snow the results of the laboratory tests and
test series forming the basis of the invention.
[0037] The corrosion protection effect of various duplex systems
suitable for application on offshore wind energy plants was
investigated in the laboratory tests. Particular attention was paid
to the embodiment of the metallisations.
[0038] In the case of the pore-richer arc-sprayed anticorrosive
coatings, a sealer serves to seal the anticorrosive coating in
order to prevent the penetration of moisture.
[0039] The various anticorrosive coatings were prepared for the
laboratory tests according to ISO 20340 with artificial damage
(scratch) with an extension of 30 mm long and 2 mm wide
(horizontal), in order to simulate damage to the corrosion
protection system, and were subjected to a 25 week cyclical ageing
test. The evaluation criteria for the quality of the various
anticorrosive coatings were the degree of corrosion from the
scratch, as well as the degree of blistering, the degree of rust,
she degree of cracking, the degree of delamination and the degree
of infiltration from the scratch.
[0040] Compared to anticorrosive coatings that had not been
deposited by thermal spraying, in particular with a reducing gas
component, a much better corrosion behaviour can be shown.
Considerable differences in the various anticorrosive coatings were
also able to be established with regard to corrosion and the
influence on the bond with a coloured layer.
[0041] The arc-sprayed aluminium-zinc coating with a layer
thickness of 75 .mu.m displayed the best results in the tests. Red
rust was formed here only in the vicinity of the scratch. An
arc-sprayed aluminium-zinc coating with a layer thickness of 50
.mu.m, on the other hand, starts with the for/nation of red rust
after approx. 16 weeks.
[0042] FIG. 1 shows a component without an anticorrosive coating
that has also undergone the laboratory tests described above. As
can be seen in FIG. 1, the component without an anticorrosive
coating has been affected after 25 weeks by marked red rust
proceeding from the crack and penetrating deep into the base
material.
[0043] FIG. 2 represents a 75 .mu.m thick aluminium-zinc coating
which has been deposited by arc spraying with air as a carrier gas
and has also undergone the laboratory tests described above. The
protective aluminium-zinc coating shows (also after 25 weeks) an
improvement compared to the component without an anticorrosive
coating from FIG. 1. The aluminium-zinc coating protects the
surface areas of the component, but proceeding from the scratch
marked red rust formation continuing into the surface can however
be seen.
[0044] FIG. 3 shows the aluminium-zinc coating with a 75 .mu.m
layer thickness arc-sprayed using a hydrogen-nitrogen gas mixture
in the sense of the invention, which has undergone the laboratory
tests described above. It can clearly be seen that the scratch is
completely protected after 25 weeks and only slight oxide formation
at several points is present. FIG. 4 shows a ground section through
the scratch from FIG. 3. The almost white oxide layer at the
surface is washed into the defect and thus protects the latter. It
is also possible to see the aluminium oxide layer, which protects
the underlying aluminium-zinc coating.
[0045] Following the 25 week ageing test, the various anticorrosive
coatings underwent pull-off tests to evaluate the adhesiveness,
Without anticorrosive coatings, the adhesiveness lies at values of,
on average, 3.4 MPa. The aluminium-zinc coating deposited by means
of air as a carrier gas has an adhesiveness of 4.8 MPa. The
aluminium-zinc coating deposited by means of the hydrogen-nitrogen
gas mixture achieves the best values. The adhesiveness of said
aluminium-zinc coating lies on average at 7.6 MPa, The reason for
these higher values is to be found in the better anchoring of the
organic coating.
* * * * *