Chromate Conversion CoatingWhen Bonding and Corrosion is
Critical
• MIL-C-5541 Class 1A & 3
• AMS 2473 & AMS 2474
• DFI’s chromate conversion coating leaves no measurable
build-up on the part and provides excellent corrosion resistance.
In many paint or adhesive applications, chromate is used as a base
for superior bonding. The coating is conductive and offered in
yellow iridescent to clear iridescent. Electrical resistance
increases with the darkness of the yellow color.
Applying chromate solution to clean aluminum produces a thin,
gel-like film, which is an integral part of the metal itself, but
converted to a non-metallic form.
Chromate treatments (sometimes called chemical film) produce
effective paint bonds through molecular adhesions with the film
being bound to the metal, in turn offering the same type of
adhesion to the organic coating. The film lengthens the life of the
paint, forming an effective barrier against corrosive attack
through pores or scratches in the paint.
Call DiFruscia Industries to discuss your metal finishing needs
or visit our website: at www.difruscia.com*Individual results may
very depending on substrate alloy and coating thickness
Technical Bulletin
TCP-HF CONVERSION COATING™Hexavalent Chromium Free Conversion
Coating
TCP-HF Conversion Coating™ matches or exceeds properties of
conventional Cr(6) conversion coatings,including bare (unpainted)
corrosion protection.
TCP-HF Conversion Coating™ offers the following advantages:
• Replacement for conventional hexavalent chromate
conversion
• Environmentally safe (compliant with RoHS, ELV and WEEE
directives)
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Chromate Conversion CoatingWhen Bonding and Corrosion is
Critical
(continued from previous page)
The great range of aluminum alloys creates a corresponding
variation in appearance ofchromate coatings. Using a given set of
treatment conditions, five treated alloys could produce colors from
pale yellow to deep brown. A high silicon aluminum casting and a
low silicon wrought product could have widely different hues.
Colors of coatings on "as-cast" surfaces are usually much lighter
than those on wrought alloys. The thickness of the film is .00001"
to .00003". This coating is amorphous (which permits cold forming
without rupture of the film) and non-porous (which aids against
corrosion).
In spite of the fact that chromate doesn't have the hardness of
an anodized finish, it stands up fairly well against abrasion of a
non-cutting nature. An important quality for chromate coating is
its ability to heal scratches in the film. The exposed metal
gradually becomes covered by soluble chromate for areas surrounding
the scratch.
Chromate films have low electrical resistance, varying slightly
between Class 1A and Class 3, with Class 3 being the most
electrically conductive. The film retards electrical action between
dissimilar metals. For maximum protection, both parts should be
chromated.
Chromate baths are operated at room temperature. Parts must not
be subject to temperatures in excess of 140° F or a breakdown in
corrosion resistance results. Proper cleaning of the aluminum is
essential in the chromating process. Oil, grease and other soils
must becompletely removed. Proprietary-inhibited alkaline cleaning
compounds can be used for soakcleaning. Most aluminum alloying
ingredients that produce smut on aluminum can be removed from
etched surfaces with a proprietary acid deoxidizer. Where
dimensional tolerances permit, caustic etching imparts a pleasing
appearance to the aluminum surface.
Call DiFruscia Industries to discuss your metal finishing needs
or visit our website: at www.difruscia.com*Individual results may
very depending on substrate alloy and coating thickness
Technical Bulletin
• Meets or exceeds MIL-C 5541 for bare (unpainted) corrosion
resistance
• Low contact resistance: meets electrical conductivity
requirements on aluminum substrates, per MIL-C 5541 class 3
• Meets paint adhesion requirements per MIL-C 5541 Surfaces
treated with the TCP-HPConversion Coating™ process are generally a
faint blue to tan and iridescent.
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