Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Can you use Alodine/Iridite/Chromates on magnesium?
Q. Can I use Alodine 1201 ⇦ this on eBay or Amazon [affil links] after prepping with Alumiprep 33 ⇦ this on eBay or Amazon [affil links] on a magnesium casting on my airplane to stop corrosion? Can I then powdercoat it to further protect it and, of course, add the beauty of powder without painting? Is there another product which can be used to corrosion coat the magnesium before powder coating?
David S [last name deleted for privacy by Editor]- Dallas, Texas
2001
Q. I am wondering if anyone has ever used an Alodine type finish on a magnesium alloy. The reason is I am trying to comply with a customer specification which requires that magnesium alloy conforming to SAE-AMS4376 be treated with material conforming to MIL-C-81706 Class 1A. This doesn't make much sense to me since MIL-C-81706 is a specification for "Chemical Conversion Materials for Coating Aluminum and Aluminum Alloys". It also doesn't seem wise to me to drop magnesium into an acidic solution.
If anyone has experience in this area I would appreciate any suggestions.
H. KinneyAdvanced Chemistry and Technology - Garden Grove, California, USA
|
A. Sir, We do aluminum finishing here as well. Until last year, we also did mag finishing for over 40 years. There are special solutions for conversion coatings on mag like Iridite #15, etc. I do not suggest using an Alodine product which is formulated for aluminum. David A. Kraft- Long Island City, New York A. I think they are referring to another type of chemical treatment..The company where I used to work do this with a solution of sodium dichromate, compound of fluoride and chromic acid, etc. We did this at near boiling temp. The resulting color is dark brown/gray. I'm sure the specs for this can be found in ASTM. Dado Macapagal- Toronto, Ont., Canada |
Corrosion Rate of Alodined magnesium
Q. Currently we have a PDA frame made of Magnesium AZ91D finished with Alodine 5200 coating.
Will like to find out what is the corrosion rate when coated with Alodine 5200?
electronics - Singapore
2003
A. How are you! Alodine 5200 is non-chrome conversion coating agent. I did test it before. I found poorer result of salt spray than chromate coating. I think non-chrome conversion coatings on Al, Mg have a lower resistance than chromate coatings.
SE DO JANG- Korea
A. Jeremy,
What is the environment for this component? As Mr. Jang said, Alodine 5200 does not provide good resistance to corrosion in a salt spray environment. However, it may provide adequate corrosion resistance in normal ambient environments (humid air, low salt, etc.). Alodine 5200 is usually used as a pretreatment prior to painting. The combination of Alodine 5200 with either a cathodic epoxy electrocoat (e-coat) or a polymer powder coating (epoxy or polyester) can provide resistance to corrosion in salt spray environments. Damage to the relatively thin e-coat layer can produce premature corrosion. Thick powder coatings usually provide much better corrosion resistance than just e-coat.
Toby Padfield- Michigan
Need Alodine 5200 applied on magnesium AZ91E alloy
RFQ: We are looking for a supplier who can apply Alodine 5200 on AZ91E magnesium sand castings.
Looking for someone to handle small runs approx. 10-100 parts lots.
Located in eastern Canada.
Magnesium foundry - Quebec, Canada
2005
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Chromating of Die Cast Magnesium Castings
Q. I am manufacturer of Magnesium Alloy AZ91 Castings by Pressure Die Casting route.These castings after fettling, do not get the golden yellow colour after conductive chromating.However if the same casting is Machined a bit, It attains the Golden colour readily.
Will someone help me in overcoming this problem?
Manufacturer - Hyderabad, INDIA
May 20, 2009
A. You don't give many particulars about your process but it sounds like you haven't removed the oxide layer prior to your chromating. A good etch should take care of that. Check with your local chemical supplier for recommendations.
Tim Hamlett, CEF
- West Palm Beach, Florida, USA
Seeking Alternative to Magna-Dyne Magnesium Conversion Coating for Bare Magnesium
Q. Greetings to all!
I am in the process of a DIY refurbishment of a set of vintage magnesium automobile wheels. Plan is to strip down to bare metal, then treat with a conversion coating, followed by a zinc dust
⇦ this on
eBay or
Amazon [affil links]
, and finally a top finish paint coat. I've done this same work in the past, and have been well pleased with the results.
However, the problem today is that the conversion coating that I have used in the past, Magna-Dyne E-2390 as manufactured by PolyFiber, has apparently been recently discontinued. PolyFiber's website notes this fact and further states that they are unaware of a similar magnesium-specific substitute which is still available.
Trying to do some research, some potential candidates which have been suggested to me are PreKote by Pantheon Chemical, and Alodine 1201
⇦ this on
eBay
or
Amazon [affil links] .
So, my question: Are either of these candidates potential like substitutes for the Magna-Dyne? And if not, can anyone recommend something else that would be?
Thanks and Cheers - DM
DIY Hobbyist - Central Ohio USA
November 24, 2009
A. Dave,
Just in case you haven't found an answer yet, The Prekote is what you're looking for. It's good for Magnesium. The Alodine is an aluminum specific product and will not do the conversion on Magnesium.
- Thomaston, Georgia, USA
by Dow Chemical Co.
is sometimes available on
AbeBooks,
eBay, or
Amazon
... but if not, you can find libraries which have copies on WorldCat.org
(affil links)
A. Hi Dave. Alodine 1201
⇦ this on
eBay
or
Amazon [affil links] is for aluminum, not magnesium. But Alodine 5200 is for magnesium. Please see our library article "Finishing of Magnesium" for a number of alternatives. And if you can find a copy, Dow's handbook on magnesium finishing.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Removing Alodine from magnesium components
Q. We have a considerable number of Magnesium AZ91D parts that were finished with Alodine 5200. We had these parts reworked and finished with NH35.
What process should be followed to remove the Alodine 5200?
If the Alodine 5200 were not completely removed before the NH35 processing, what would be the result? Would there be a degradation in the coating over time, or would the NH35 simply not react at all?
Manufacturing engineer - Hope Hull, Alabama
February 2, 2010
Q. I wish to paint by brush my magnesium Halibrand wheels on the inner rim to prevent air loss. Is Alodine 1201 recommended as a precleaner prior to epoxy primer and then epoxy top coat?. The wheels are from an original Cobra 427.
Barry SimmonsDr. Barry D. Simmons DDS PC - Athens, Georgia USA
April 2, 2017
A. Hello. We appended your inquiry to a thread on the subject of pretreating magnesium. Alodine 1201 is for aluminum and will not properly pretreat magnesium. Alodine 5200 (if you can find it) or PreKote sound like a better idea. But the wheels should be carefully cleaned first because these processes are corrosion-fighting, bonding pretreatments, not cleaners.
You might also find letter 03, "Coating/restoring Halibrand wheels; history of magnesium wheels" interesting. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Ted, I find nothing in the Alodine 5200 documentation that mentions that it may be used on Magnesium. Can you point me in the right direction? Thank you.
Bruce Bodger- Oklahoma City, Oklahoma, USA
October 25, 2017
A. Hi Bruce. Henkel tells us in their sales literature that it is for "light metals" rather than saying it's only for aluminum. Their RoHS compliance statement says that Alodine 5200 complies, from which we can deduce that it is chromate free. They tell us in the D.O.D. section of their Safety Data Sheet that it contains fluorotitanic acid, from which we can deduce that it is probably a titanium-based or zirconium-titanium based coating.
Two readers on this page say they've used it on magnesium; one says it's not as corrosion resistant as chrome-based coatings.
A reader on thread 53759 says he uses it on magnesium.
A reader on thread 25020 says it's not as good on magnesium as chromium treatment.
Beyond that it's probably up to Henkel, not the rest of us, because not only is the product trade secret, so we can't reliably know that all of its ingredients are appropriate for magnesium under all circumstances, but they own the tradename and are free to change the formulation at any time anyway :-)
Please introduce yourself and tell us what you're up to -- this forum tries to be a roundtable, not a lecture hall :-)
Thanks!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Thank you for the reply, Ted. We're in the aviation industry and since I can find no affirmative mention that it's APPROVED for use on Magnesium aircraft applications we have to presume that it is not. (Safety first, you know :-)) We were looking for a pre-treatment for a localized repair of a Rockhard coated magnesium gearbox. Pratt does provide a SPOP for the pre-treatment however it would be a nightmare to mix up a small quantity.
And as far as what we do... we manufacture, distribute, and apply Ceral coatings onto A/C compressor parts.
~Bruce
- Oklahoma City, Oklahoma, USA
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