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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 2018



"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".

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

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 - Idaho


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


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,] 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, Teds signature
Ted Mooney, P.E.
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.


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

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