plating, anodizing, & finishing Q&As since 1989
Zinc phosphate coatings as deterrent to galvanic corrosion
Q. Are there any studies evaluating the effectiveness of zinc phosphate coating ( MIL-PRF-16173 [affil link or from DLA, type 1) as a deterrent to galvanic corrosion? Are there any data on the conductivity of zinc phosphate coatings?Evan Gabrielsen
A. Companies that sell phosphate should be able to provide you with this information and platers that use their product in your area if you are not going to do it yourself.
As I remember, the Rock Island Arsenal is the godparent of that Spec. One or more people from there have written articles in trade pubs. Check Metal Finishing and Plating & Surface Finishing magazines for the last five years. There is a several page article in one of them.
You can very possibly get help from the Arsenal also.
NACE, National Association of Corrosion Engineers would have back conference articles for sale I think.
It is good stuff, especially as a paint base.James Watts
- Navarre, Florida
A. Zinc phosphate has been primarily developed as a environmental friendly substitute to zinc chrome for corrosion protection . this property comes by its resistance property .ulhas joshi
Q. Are there any studies using zinc phosphate coatings as a barrier layer between Cu and Au to minimize or eliminate galvanic coupling reactions during wet etching? Does anyone have any suggestions as to minimize this problem? Thank you,Mitchell Koblis
- San Jose, California
Q. We have problem with the galvanised reinforcing steel we are using in our concrete products. We have been using chromium trioxide to passivate the zinc so that hydrogen gas is not released that weakens the bond. How ever we are looking for a substitute admixture of Chromium trioxide to avoid the health and handling hazards.
Any suggestions will be very useful.
Thank you.Dhanada Mishra
- Guldford, NSW, Australia
Q. I was wondering for typical zinc phosphate solution what are the typically specifications. Is their any need for an anion free zinc phosphate solution?Keith Kujawa
- LaSalle Illinois
I think that if you are using now ,some coating ,probably you must be use a cold roll steel with a Tri-cationic Zinc Phosphate ( this phosphate have the following properties , crystal size between 2 and 6 microns and coating weight between 120 and 250 mg/sq feet )because you have the most rust protect un-blistering the piece . The blister is more common that appear in the 300 or 350 hour in salt spray for galvanize steel .
Excuse my english
I Hope that you can understand me .Rebolloso Gerardo
- Mexico City, DF, Mexico
Q. I am looking for a plating or coating for a steel screw that will protect against galvanic corrosion when the screw is used in a magnesium housing. Any information on this topic will be greatly appreciated.Brian Abrams
- Syracuse, New York
A. I may be misunderstanding you, Mr. Abrams, but a steel screw (or any common metal for that matter) will be cathodic to magnesium and will be in no danger of galvanic corrosion. The housing is what will corrode, and there is no way to protect it by plating the screw. I would consider electroless nickel plating the housing.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. What is activated zinc phosphate? What is complex forming type zinc phosphate? If you could answer these questions I would be pleased very much.
Thanks in advance,Sinan Kocaman
- Istanbul, Turkey
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