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SYNTHESIS
=-——c
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REPoI<rr
FOR H_H31JCATK)N
CON.TRACT N“ :
BRE 2 - CT 94 - 1423
PROJECr No :
CR - 1381 - 91
T TJ_E ;
Development, of repair procedures and
regulations for the repair of corroded
aluminium, especially damaged by filifurm
corrosion.
PROJECYCOORDIXATOR : “
PARTNERS
und
Forsehungsinstitut fur
(D)
Edelmetalle
Metallchemie
ALSAN Alvarez Schaer (E)
Alumax (NL)
Ambruch Fassadenpflege (D)
M.I.M. (F)
Munk Gmbli (D)
Racieburger Fensterbau (E)
Verniciatura Industrial ‘deneta (1)
STARTING DATE :
i
FEPI,
01.10.9:4
DURATIOli
~:
: 24 ~,n~hs
J
.—
DATE :
30.09.96
Development of repair procedures and regulations for the repair of corr~dted
aluminium, especially damaged by filiform corrosion
Dipl.-lng. (FH) Jorg Freudenberger
FEM, KatharinenstraBe d?, 73525 Schwabisch Gmtind
1. Abstract:
1
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In architecture and in the automobile industry, coated aluminium is being applied more and
more frequently. In architecture aluminium is appreciated because of its va’ious decorative
possibilities which a coating with organic materials offers. In the automobile industry, emted
a[uminium is being applied more and more frequently because of its minimal weight and the
possibility of a complete recycling. Due to the increasing air pollution, new areas of
application and new and various locations, the demands on the corrosion protection that the
material should guarantee are also increasing.
In certain areas of application and at certain [ocations, the system is overtaxed, and
corrosion occurs already after a short time (1-2 years). By guarantee obligations of 5 years,
it is the responsibility of the manufacturers to repair the corrosion damages.
Until now approx. 40 million ECU were used to repair components which had been ~
damaged by corrosion, above all filiform corrosion. As a rule, these repaired components
show corrosion again after approx. 1-2 years, and the treatment must be repsated.
The development of a cost effective, environmentally protective repair-system %vxdd
facilitate an enormous reduction in costs and a lasting repair of the corroded compon=r% of
coated aluminium, and should prevent a further corrosion attack and thus a quality
reduction of building components.
The core of the new repair-system developed in this project is an anodi; alurninium-cxide
layer which can prevent filiform corrosion almost completely. This corrosicm-protective and
adhesion-promoting under-[ayer for the coating is formed on the ground Al-surface to be
repaired with a portable anodizing equipment developed for the employment on the sp~~ a[l
other operations of the repair (mechanical pre-treatment, coating) are the same as in the
repair-procedures until now.
The testing of the repair system ensued with selected coating systems in laboratory and in
field experiments. A noticeable improvement of the corrosion- (especially tiliform corrosion-)
resistance compared to the repair-procedures until now was found in the !atmratory tests,
The field experiments are carried out on various damaged components ~f bui!dings iocated
within Europe.
The results of this project were carried over into the elaboration of new regulations cm the
carrying out of repairs of damaged and/or corroded coated aluminium components.
2. Introduction
The demands on preventing corrosion of coated aluminium have been ccmstantly g~awing
over the last few years on account of new applications, new locatians and increasing
environmental pollution. The state of the art in Europe and worldwide is ihe app!icat;on of
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chromated and coated aluminium, In the construction industry e.g., the lifetime Qf a facede
is supposed to be 30 years, In many cases, above all in maritime climates and in ~~aas
where industry and maritime climates coincide, these systems are overtaxed and show
corrosion damages already after a short time {1-3 years, depending cm the Ioca%n).
Guarantees for the lifetime of coated aluminium-components of a minimum of 5 years,
rising up to 10 years are usual in the metalworking industry nowadays; the existing repair
systems can only prevent the renewed corrosion for a very short time (approx. 1-2 years,
depending on the location).
A certain type of corrosion which forms characteristic fibrils, the so-called filiform corrmion,
has been appearing more and more often over the last few years. Filiform corrosion mahly
starts in faulty areas on the coating, drainage slots, edges, drilled holes and mitres. A
component affected by filiform corrosion is not expected to lose mechanical strengt: ~, but
the external appearance of the facade is adversely affected. If all damage which had
occurred previously was to be treated or those parts of the facade recoated then a stim of
approx. f100 million Dfvl would certainly not be enough for this.
Experience shows, that the filiform corrosion occurs under certain condkiom. Included in
the factors which cause corrosion are first of aH a high atmospheric ?w..midity and the
presence of conducting ions (salts), particu[arfy chlorides and sulphates. Thsse ions can get
under the coating; together with water and oxygen a corrosion cell is formed which moves
slowly and forms the typical fibrils.
It has been demonstrated in laboratory tests and is being futiher deve[oped and tested at
the moment in an other CRAFT-Project, that the anodization as a pretreatment is a very
good method for the avoidance of fi[iform corrosion, However, this kind of pretreatment was
not possible until now for the use on the spot in the field of the building in~ustry by means
of the conventional technology. Thus, the necessity of testing new and speciai methods
ensued. The development of a portable anodization equipment with which an anodic Ioxide
layer can be produced on building components on the spot, is one such new procedure.
The main objective of this project was to develop a repair method offering a lasting
corrosion protection which can prevent particularly filiform corrosion in coastal areas and
which thus can avoid a reduction of quality and decorative appearance of the building
components. The repair system developed had to be tested in laboratory and fietd
experiments; the corrosion resistance of repaired aluminium samples had to be tes%d in
corrosion- and accelerated weathering tests in the laboratory as we!l as in long-term
outdoor-exposure tests at locations with different climates throughout Eurq,~.
3. Technical description
3.1 Literature research
A literature research at the start of the project about the topics fiiiform corrosion on
alurniniumt coating, repair of coated parts and anodizing (electrolytes, bmsh anodizing) was
carried out.
The research showed that no relevant work on the applicability and/or corrosion resistance
of coating systems for use as a repair system exists until now.
3.2 Determination of the actual status
The objective of this part of the project was a listing and comparison of the repair systems
(primers and top-coatings customary in the trade) applied until now, testing their propelies
and comparing the repair systems to industrial coating systems.
The substantial difference is the chemical pretreatment (chromating) whicti is only a~plied
at the industrial coating. Regarding the corrosion inhibition, the chrcxnafe layer can
approximately be compared with pre-anodized oxide layers; in pilot tests the preanodization showed equal or even better results than the chromating.
e
In most cases (about 95 /0) powder coatings are used for the industrial coating; for a fispair
on the spot, however, the application and curing of powder coatings would not be p~ssible.
Therefore, all coating systems tested were air-drying Z-components liquid [RJR-,
epoxy resin- or phenolresin-; partly with zinc-powder) primers and (PLJR-, PVEW-, or
acrylate/isocyanate-) top-coats.
The coated samples were tested on their mechanical / technological properties and m their
corrosion resistance.
0
a
b
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The coating systems were applied on the aluminium alloys AIMgl (sheet-materk) and
AIMgSiO.5 (profile-material) which are the most frequent Al-alloys in the building trade.
The coating systems to be tested were applied directly on the (degreased and pickled)
aluminium samples. in comparison to the repair systems, the coating systems were also
applied on (yellow-)chromated samples which represent the industrial systems. Chro-.ating
as pretreatment is the state of the art in the industrial coating of aluminiwa; the corrosion
resistance and the mechanical properties like e.g. the adhesion of the coating are increased
considerably by the chromate layer. However, it is not possible to chrom~ate a pafi to be
repaired on the spot; furthermore, chromating solutions are toxic, carcin~genic and harmful
to the environment because of their content of hexavalent chromium (for this reasen the
industry endeavors now to find adequate substitution for the chromating). There are also
primers with a content of hexavalent chromium which may be used for the repair, but they
were not taken into consideration within this project because of their harm to health and
environment.
F“
/
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Mechanical tests:
- Cross-cut test (DIN .53 151)
- Bending test (DIN 53 152)
- Erichsen cupping test (1S0 1520)
- Boiling test (Regulation of the GSB international]
- Combined boiling / cross cut test
Corrosion tests:
- Salt spray test (DIN 50021 SS); 1000 h
- Acetic acid salt spray test (DIN 50021 ESSJ; 1000 h
- Test in condensate water alternating atmosphere containing S02 (DIN !50018 SFW 0.2 S};
30 cycles
- Test in condensate water constant climate (DIN500~7 KK); 1000 h
- Filiform cocrosion test (DIN 65 472); 1000 h
3
In addition, some new combinations of primers and top coats were tested as well as a new
chromium-free chemical pretreatment basing on titanium. The sampling and testing was
carried out as described above.
3.3 Development of an anodization process to be applied on the spot
It is known that anodic oxide layers (with a layer thickness of at least 5 j.un) as under-!syers
for coatings on aluminium provide a very good corrosion resistance, particularly against
fi[iform corrosion. With regard to the corrosion resistance, the anodic oxide layer can
approximately be compared to a chromate layefi if such an oxide layer cculc.i be forrr~ti on
an area to be repaired, the repair system to be developed could, in Contrenj to the repair
systems until now, approximately reach the quality of industrial coating systems. Therefore,
the core of the project was to develop a portable anodizing equipment to be applied cn the
spot, the development of an appropriate electrolyte, the determination af the anodization
parameters and the working-out of regulations for the repair.
Industrial anodization is carried out in tanks containing the electrolyte; so the first idea for
the anodizing on the spot was, similar to the industrial anodizing, to put a ~~idl tank %%hout
a bottom, filled with electrolyte and a cathode, on the area to be repaired @vhich is the
anode). Tests with a cell made out of plastic and sealing cement showed that it wcwki be
almost impossible to prevent a leakage of the electrolyte; furthermore, the geometry of the
parts to be repaired was a problem. In practice, the areas to be treated, e.g. on faudes,
door- and window-frames’ are formed differently and often lie in corners or angles. The cell
should therefore be flexible and adjustable to the different geometries whiie having a good
sealing. Since these requirements seemed impossible to meet with a real ce!l, the brush- (or
tampon-] anodizing procedure was selected, At this procedure, the electmtyte is not fiiied in
a cell, container, or tank but is soaked in an absorbing tampon-materiai like e.g. c!oths,
sponges etc. which is wrapped around a solid, current conducting material with an insulated
handle setving as cathode. To avoid a dropping of the electrolyte, a thickening agent had to
be found making the electrolyte high-viscous and therefore appropriate far the use e%sn on
vertical areas.
The tampon-anodizing procedure for the use on the spot was developed by testing di%?rent
possibilities of each component (electrolyte, cathodes, tampon material...) and detmnining
the most suitable one:
Eiectroiyfe:
The requirements for the electrolyte, among others, were:
- greatest possible harmlessness (non-toxicity, pH-value in a moderate area {4-10))
- simple handling
- voltage must not exceed 25 V (due to legal regulations)
In a series of tests AIMgl-sheet samples were anodized (with the tank- and/or brushanodizing procedure) with a number of different anodizing electrolyte. Amcmg the
electrolytes tested were usual in industry ones as well as rarely used ones described in the
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literature; most were basing cm organic or inorganic acids, but ah some alkaline
electrolytes were tested.
While testing the electrolytes also different methods of cleaning (decreasing) before the
anodizing and anodizing parameters (current density, voltage, time, m,ovement cl? the
cathode etc.) were tested
Tampon-material:
The main requirements for the tampon material were:
- acid-resistance
- absorption power
- handling
Among the tested materials were cloths made of different materials (synthet;:s and na2~ral,
e.g. cotton...), sponges (synthetic, hard, soft, with different size of the pares... ) and other
(e.g. paper-like as used for filtration) materials.
T h i c k e n i n g agent:
A lot of thickening agents, gelling agents and similar substances were testd on their
- acid-resistance
- thickening power, also under mechanical stress
- the influence on the conductivity K and the p!-1-value of the electrolyte
- non-toxicity, environmental compatibility
- concentration necessary, cost effectiveness
Most thickening agents tested were natural organic products from different plants, fruits,
algas etc., but also synthetic and inorganic thickening were tested.
Cathode and handle:
Most cathodes and handles tested were industrially manufactured; the cathode matefial, in
most cases graphite or stainless steel is normally acid-resistant, but also aluminiurm could
be used.
Recfifiec
The rectifier changing the A.C. from the mains into D.C. necessary for fhe anodization, is
the most important part “of the portable anodizing equipment. Rectifiers are norrnaiiy very
heavy and therefore not appropriate for the use on the spot. Therefore$ a rectifier which
meets the following properties had to be developed:
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it should correspond to the accident prevention- and safety-measures
it should be light and small
it should contain current- and voltage-regulation and be absolutely shoti-ckcuit-resistzmt
integrated options: ampere-minutes-counter, timer
installation of an outlet for other machines
Under consideration of the above demands, a rectifier was developed w;th a performance
of 20 V / 20 A; weight about 7 kg.
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3.4 Testing of the repair system in laboratory experiments
The applicability, handling and degree of effectiveness of the repair system as well GS the
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,., .
corrosion resistance and the mechanical properties of me
“ sampies repawea were tes=aa m
the Iaboratoty,
Sampling:
The samples {profiles and sheets) have been coated industrially (chromated and powdercoated according to the state of the art). Then the profiles were assemb]ad to F-shaped
samples and provided with water drain slots. These F-samples show therefore the typical
spots (mitre, obtuse connection, water drain slots) where fdiform corrosion c>ri window- and
door-frames often starts.
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F~gure 1: The F - shaped profile-samples (made of common profiles for window frames;
industrially coated (chromated + powder coated) and assembled) imitate” a window- or a
door-frame:
R ‘r’ ’dhe’e
(for hanging the sampie.s)
water drain slot (punched)
F+05tuseJ0int
water drain slot (milled)
mitre
a
The dimensions of the sample are: length: 370 mm, width: 270 mm;
width of the profile:l 00 mm
Two coating systems which offer a good corrosion protection have been chosen for the
repair. The repair is carried out as follows (it is the usual procedure of a repair as earned out
until now, only the anodizing-operation with the portable anodizing equipment was
integrated in this existing sequence of operations):
- Grinding of the powder-coating on the areas to be repaired down to the basis met.&
- Roughening of the remaining coating
- Cleaning (washing, rinsing, decreasing)
- Tampon anodization: the parameters depend on the area to be anodized. The area to be
anodized should not be larger than 1 dmz; anodizing time is about t = ~D - ‘12 rein; anodic
current density about i = fl .5-1.8 A/dm2; voltage about 15 V; required layer $!hickness > 5pm
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- Removal of the thickened electrolyte from the surface of the part; the e!ectroUyte c=- be
reused
- Washing, rinsing and drying of the surface
- Checking of the layer-thickness
- Priming of the anodized areas
- Polishing (wet) of the primer-layer
- Coating of the complete surface with a 2-components air-drying [iquid lacquer
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Tesfing of fhe mechanic pmperfies and corrosion n?sisfance:
The same mechanical and corrosion tests as described in section 3.2 (Determination of the
actual status) were carried out,
3.5 Outdoor exposure of the samples in different climatic regions
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The objective of this part is the examination of the corrosion behaviour of the different
repair-{coating-) systems in various climatic regions and the determination of the correction
between results of the laboratory experiments and results of the outdoor exposure.
The samples (sheets and F-shaped profiles) were manufactured and repaired the same
way like the samples for the corrosion tests in laboratory, As locations for fhe outdoor
exposure were chosen:
Venice (Fusina) / Italy
Naatdwijk (Hock van Holland)/ The Netherlands
Lauchheim / {Southern-) Germany
in a former CRAFT project about filiform corrosion, outdoor exposure tests with mated
aluminium sheets were carried out on many coastal locations throughout Europe. These
tests are not finished completely yet, but first evaluations allowed to put up a ranking M of
the locations where filiform corrosion grows best. The most aggressive clirnat~c conditions
were found at the locations Venice (Italy) and Naaldwijk (Netherlands), so these two
locations show results after a relative short time and were therefore chosen for the outdoor
exposure of the samples of this project. The third location, Lauchheim (Sm-khern Germany),
offers a completely different climate. H is more than 600 kilometres away from the sea and
has only a very slight industrial atmosphere; no attack by chlorides, su[phates or other
corrosion-starting ions is expected, but it has, in contrary to the c~astal locations, a
continental climate with rel, hot summers and rel. cold winters. These temperature
differences are also a stress for coatings.
3.6 Field experiments with the systems that have been tested in the laboratory
The applicability of the repair system was tested under realistic circumstances on different
parts damaged by filiform corrosion at locations throughout Europe. The repair system was
assessed in the criterions handling, working method, costs, time, optical impression Qf the
repaired components and lifetime without corrosion of the repaired parts.
4. Results
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The determination of the actual status of 2-component liquid coatings on ~hromated and
non chromated aluminium samples showed, as expected, that chromatec! samples had
better (or at least the same) results in the mechanical and corrosion tests. The results of the
different coating systems varied greatly, each system had pros and cons. in the dif%rent
tests; therefore it was not possible to name one coating system as the ,,best”. Due to the
results of this series of tests, two coating systems with different properties were selected for
the use as repair coatings on the anodized repair-areas: repair-system #l had very good
results in the filiform corrosion test, even on the non-chromated sarnpies, but worse
adhesion, particularly in moist atmosphere. The primer / coating combineticm # 2 had only
average results in the filiform corrosion test, but a very good adhesion even in moist
atmosphere.
The portable anodizing equipment developed did meet all requirements for the use cm the
spot. The thickened electrolyte had a good conductivity, so on!y a rel. low voltage oc~~rs (it
only was not possible to find an appropriate electrolyte with an moderat~ pH-value: the
electrolyte selected has a pH-value < ~}. The thickening agent was completely acid resistant
and had a high thickening power. As cathode-material graphite-bars of different siz~s and
forms were very appropriate; as tampon-material a special cloth, strongly fringed, with a
large surface and absorbing power was selected. As D. C.-source sewed the rectifier
developed.
The complete portable anodizing equipment (rectifier, thickened electrolyte, cleaning
solutions, cathodes and tampon material, various tools (cables, clamps, wipers etc.) .as well
as the protection equipment (gloves, glasses) necessary when handling with the acid
electrolyte) is put in a stable alurninium-case. The anodizing equipmeni can easi!y be
transported this way and used on each location where a 230 V connection is available.
The results of the corrosion tests in the laboratory showed a considerable improvement of
the corrosion resistance of samples with the new repair system developed c>ompared to the
repair systems (without a pre-anodization layer) applied until now alse the mecnankal
properties ‘where partly slightly better. The both repair systems tested were combinations of
a primer and a top-coat. The top-coat can also be applied direct on the anodic oxide %yer,
without a primer. Filiform corrosion tests in the laborato~ were carried out with t==ponanodized samples (thickness of the anodic oxide layer about 5 pm) directly coatW with
liquid air-drying 2-component PUR- and PVDF-coating. Result after 1000 h: no corroskm.
Results of the outdoor exposure test of the repaired samples are not avai;able yet.
In field tests on different locations the repair system was tested by workmen and assessed
on different criterions. Handling and working method were classed as very good. The only
point criticized was the time spent (and therefore the personnel costs): the time for the
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anodizing is about 10 rein, with cleaning and rinsing before and after the aficdization about
15 min for each spot to be repaired.
5. Conclusions
A new, practicable, non-polluting {chromium-free) repair system for darn=ged, corroded
(especially by filiform corrosion), coated aluminium-components was developed.
The mechanical properties and the corrosion resistance of samples were tested which were
industrially coated or repaired with the repair procedure until now or repaired with the new
repair system. Compared to the repair systems until now, a considerabbs improvement of
the corrosion resistance (especially against filiform corrosion) of samples repaired with the
new repair system was determined .
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The sequence of operations at the new repair system is almost the same as at the repair
systems until now (mechanical pretreatment - cleaning - coating). Only one step was aflded:
before coating, an anodic oxide layer with a layer thickness of at least 5 Km is formed by
means of the brush- (or tampon-) anodizing procedure. Therefore, the core of the new
repair system was the development of a tampon anodizing procedure appropriate fwr the
use on the spot, whereby the most important points were: development of an appropriate
rectifie~ testing of electrolytes and thickening agents; fixing of the anodizing paramete~s,
For the coating of the anodized area different top coatings or coating systems (primer+ top
coat) can be used. Two repair systems were tested on the anodic oxide layer, Twn top
coatings (a PLIR- and a PVDF- lacquer), directly applied on the anodic oxide lay=: (i.e.
without a primer-layer) where tested on their filiform corrosion resistance: even after ~ 000 h
both coatings showed no filiform corrosion. It seems that first of all the anodic oxide layer is
responsible for the good {filiform) corrosion resistance of the samples coated witin the
different coatings tested; the contribution of the coating seems to be much smaller, so not
only one certain coating or coating system but many different possibie coatings may be
used.
These results are not sufficient for a final recommendation which top coat to uss and
whether a primer is necessary (and if yes which). Laboratory tests may show a certain
tendency of the corrosion behaviour of a coating system; they can, however, never sin-date
the weathering of samples under realistic conditions. Therefore, samples repaired and
coated with the different coating systems tested in the laboratory, are tested at the rmment
in outdoor exposure tests in the Netherlands, Italy and Germany for at least 3 years. They
will be assessed regularly on their corrosion behaviour.
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6. Acknowledgements
We would like to thank the European Commission, Directorate General X11 (Science,
Research and Development), Directorate C for supporting and promoting the project
.Development of repair procedures and regulations for the repair of corroded alumivwrn,
especially damaged by filiform corrosion”, contract number BRE2 - CT94 - 1423, p;cject
rwmber CR -1381-91.
We would also like to thank the partners A. Schneider, H. Schaer, H. Mew+vissen and
Boumans, J. Schmidt, K.-H. Munk, R. Ambruch and G. Fenzi as well as Dr. P. I_ambe- and
Dr. K. Kogler for their expert advice and assistance in carrying out the work.
7. Selected references
Repair
[1]
Beschichten von Aluminium, Aluminium-Merkblatt 03, 7. Auflage, p. 11
[2] Bauschadensammlung, Hrsg. G. Zimmerman, Band 7, Forum-Verlag Stuttgart, p. 60
[3] E. V. Schmid: Wetter- und Korrosionsschutz, Curt. R. Vincentz Verlag, Hannover II 983,
p. 379
FYefreafrner)t:
[4] l-t. Simon: Vorbehandeln metallischer 0berf15chen fur das IBeschichten, Ga[vanok$mik
73 (1982) 12, p, 1320
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[5] C. Groshart: Preperaton of basis metals for painting, Metal. Finish. 58, ~WO, ~A, p. 169
[6] B. R. W. Hinton: Corrosion Prevention and Chromates, the End of an Era ?, Metal.
Finish. 89, 1991, p. 55
[7] B. R. W. Hinton e. a.: Si{ane Pretreatment for Corrosion Protection and Improved
Coating Adhesion
[8] B. A. Shaw e. a.: A Molybdate Treatment for Enhancing the Passivity of Aluminium in
Chlorid-Containing Environments, J. Electrochem. Sot., Vol 137, No. 1, 19W, p. 359
Tatnpon-Anodization:
[9] M. Rubinstein: Das Tampongalvanisieren, Eugen G. Leuze Verlag, D-Saulgau / VJurt.
1985
10
[10] M. Rubinsfein: Das Tampongalvariisieren, Band 2, Eugen G. Leuze ~e~[ag, Sau@u /
Wurt. 1994
[11] C. Norris: Brush Anodisation, [n the Aircraft / Aerospace Industries, Plat. and Surf,
Finish. (1991) 8, p.36
[12] C. Norris: Brush Plating Techniques for Salvage and Repair, Metals / Materials
Technol. Series, Paper No.: 8201-088, Hrsg: ASM, 1982, p. 1
Anodization - Electrolytes:
[13] T. Biestek, J. Weben Electrolytic and Chemical Conversion Coatings; IFkxlcullis Press
Limited - Redhill, I’t Edition (1976)
[14] F. Pearl-stein: Selection and Application of Inorganic Finishes, Part [11 - A.nodic Ccdngs
for Aluminium, Plat. and Surf. Finish, (1979)2, p. 30
[15] J. M. Kape: Anodizing in Aqueous Solutions of Organic Carboxylic Mds, Trans, IMF
45, (1967), p. 34
I
[16] J. M. Kape: Thick Oxide Films on Aluminium Alloys, Metal Industry, 9 August 1%57, p.
63
[17] J. M. Kape: Thick Oxide Films on Aluminium Alloys, Metal Industry, 16 August 1 ~57, p.
129
[18] J. M. Kape: Thick Oxide Films on Aluminium Alloys, Metal Industry, 20 September
1957, p. 239
[19] W. Htibner und C.-Th. Speiser: Die Praxis der anodischen Oxidation des Aluminums,
Aluminium-Veriag, Dusseldorf, 1988
Thickening agents:
[ 2 0 ] t - i . Rompp: Rompps Chemie-Lexikun,
Verlagshandlung, Stuttgart, 1972
Iirsg. O . - A . Neumutler, Franckh” sche
[21] Angew. Chemie, 55.Jahrg. 1942 Nr. 49 / 50, p. 377
[22] G. Lunde: Der Meerestang als Rohstoffquelle, Angew. Chemie, 50. Lahrg. 1937 Mr. 36,
p. 731
11
I%iform Comxion:
[23] G.M. Hoch, R.F. Tobias: Mechanisms of Filiform Corrosion, F%per 19, !:.4CE
Corrosion/71, 1971
[24] W.H. Slabough ea.: Filiform Corrosion of Aluminium, Journal of Paint Techology: 44,
1972
[25] H, Kaesche: Lfntersuchung uber die Filigrankorrosion Iackierter Stahlt&che, Werksfoffe
und Korrosion 11, q 959
[26] G.H. Hoch: A Review of Filiform Corosion, Int. Corros. Conf, Serv. Volume Date 1971,
NACE-3 134-42
[27] W.H. Slabough, E.J, Chan: Atmospheric Components and Filiform Canmsion, J. Paint
Techn., Vol 38, No. 499, 8, 1966
[28] W. Funke: Blistering of Paint Films and Filiform Corosion, Prog. Org. Coating, 9, 4981,
29
[29] H. Haben, K.H. Rihm: Filiformkorrosion auf organisch beschichtetem Aluminium, Farbe
+ Lack, 96, 7, 1990
{30] Gute- und Prtifvorschriften der Gutegemeinschaft sttickbeschichtetes Aluminium, RALRG 631
[31] DIN - Entwurf 65472: Prufung der Filiformkorrosionsbest~ ndigkeit
[32] J. Pietschmann, H. Pfeifer
Filiformkorrosion auf organisch beschichtetem Aluminium, Teil 1-3, Zei%chrift Alur.hium,
69, 70 (fi993/94), 1019-1023, _1081-1084. 82-86
[33] M. Heinrich e. a.: Filiformkorrosion von Aluminiumt Farbe + Lacke 100. Jahrgs-g 4 /
-1994
12