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topic 16006

Chromate conversion coating aluminum parts having inserts of steel or other metals


A discussion started in 2002 but continuing through 2019

2002

TUTORIAL FOR NEWBIES:

"Alodine" is Henkel's tradename for their line of chromate conversion coatings for aluminum. "Iridite" from MacDermid is a similar line. The process is sometimes called "chem-filming of aluminum".

Q. I deal with Alodine 1200s and my question is: Is it safe to Alodine aluminum parts which have dissimilar materials installed in them such as steel helicoils, bushings, dowel pins, etc.?

Thank You,

Mark S Draper
- Central Point, Oregon


simultaneous 2002

A. I've never had any problem with chromating parts with pins, helicoils, etc., although they have always been stainless inserts.

Marc Green
Marc Green
anodizer - Boise, Idaho


2002

A. We have Alodined parts with hardware installed. Have found that we must use stainless steel hardware because the acid cleaner and chromate solutions will attack and discolor zinc or cad plated hardware. Also must give the parts a good final rinse and blow dry the areas around the hardware to prevent any bleedout of entrapped solution.

Lee Blanton
- Denton, Texas


2002

A. To my knowledge, racking of dissimilar alloys when anodizing is not advisable. I have not heard of the same for Alodining.

Dado Macapagal
- Toronto, Ontario, Canada



August 28, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Will Chromate conversion coating to Mil-C-5541 [link is to free spec at Defense Logistics Agency, dla.mil] damage stainless steel?

We have aluminum panels that already have stainless steel pem serts installed and had to machine the panels requiring the panels to be re-plated. My question is will there be damage to the stainless steel pem serts? If so, how severe?

Keith Dutton
- Madison, Alabama


September 2, 2012

A. Hi, Keith. We appended your question to a thread where it was already answered. Looks like stainless inserts will be okay.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



Can Alodine be 'wiped on'?

August 17, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I've got some machined aluminum parts I'd like to keep looking like new. I'd probably have these anodized or simply Alodined, but steel, stainless and bronze press-in parts (bearings, bushings, dowel pins, etc.) have already been installed and would be a royal pain to remove. Can I simply use rags and Q-tips to 'wipe on' Alumiprep, rinse and then Alodine 1001, being careful to avoid non-aluminum surfaces, or is this asking for trouble? The alternative would be some sort of clear coat or wax, and I'm open to suggestions in this area too. Many thanks.

Jim Wood
Inventor/Hobbyist - Brea, California, USA


August 2018

A. Hi Jim. Yes, chromate conversion coating can be swabbed on. Some can even be allowed to "dry in place" so rinsing isn't required (see thread 10893) Further, per the thread you are reading, stainless inserts probably aren't a problem for immersion chromating, but steel and bronze probably are.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



October 9, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear Experts, I have one more doubt that we are able to yellow chromate the assembly having aluminum plate fixed with ss screws?
Whether there is any issue during the processing or coating?

Please provide your valuable comments on the above.

ADITYA MANDLIYA
Freelancer - Chennai, india


October 10, 2019

A. The process you need is: (1) typically clean in an aluminum cleaner, alkaline etch is optional, here comes the difference: deoxidize in Ferric Sulfate 8 oz/gal (nothing else), must be air agitated to keep it Ferric and not Ferrous, - it is safe on the stainless and will adequately prepare the aluminum for regular yellow chromate.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina



October 4, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can we install steel hardware before clear alodine?

Lam Ho
- Fayetteville Georgia


October 11, 2019

A. Electric motor manufacturers typically and successfully yellow chromate aluminum in the presence of imbedded mild steel. Ferric Sulfate is used for the deox and is also safe and harmless on the exposed mild steel. At least one proprietary supplier of commercial "deoxidizers" for aluminum sell plain ferric sulfate as a dry powder product for use on ALL aluminum deox conditions.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

----
Ed. note: For second opinions and additional discussions please see these related threads:
00664 "Chromate conversion coating on screwed & glued aluminum"
56597 "Can Alodine/Iridite/Chromating be done with steel inserts already in place?"

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