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Looking for a non hexavalent corrosion resistant primer for use on carbon steel

December 9, 2008


I am a Value Stream Manager for a company that manufactures drive shafts for helicopters. These are flight critical items sold directly to OEM's ( Bell, MD, Augusta Westland, etc...) I am looking for an environmentally friendly corrosion resistant coating that can be applied to carbon steels. Currently we apply zinc chromate to the I.D. of a bolt joint that is bare metal. We hand apply the zinc chromate to this area to provide corrosion protection. We are looking for an environmentally friendly alternative coating that will provide corrosion resistance and is also relatively thin when applied (a few tenths)without the hexavalent chrome. Any help would be greatly appreciated.

Thank you

Chris Crandall
coating user - Bloomfield, Connecticut, USA

simultaneous replies

It HAS to be a process that is approved by the OEM of that particular part. So what options do they give you? It is normally on the print.

James Watts
- Navarre, Florida
December 11, 2008

We looked at sol technology as an environmentally friendly coating. Using a Nano format of silanes and SiO2, the material was waterborne and if correctly formulated could be applied by dipping or spray resulting in film wts of 2-8 microns. The resultant coating film (requires baking 180 C) should have outstanding weather protection (>2000 hrs ASTM B117 [affil link] ) and exceptional abrasion resistance. Unfortunately, the solid content to achieve this (35-38%), resulted in the C.P. being too high ($20/litre) for our industrial mk place, but I would imagine not a problem if you supplied the aircraft industry (we don't) where costs are traditionally expected to be much higher

Terry Hickling
Birmingham, United Kingdom
December 11, 2008

Try website-there are some patents on use of tannin (or lignin) based solutions (modified with titanium/ fluor salts). Probably not so effective as hex chromates. Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
December 13, 2008

One more time again. It does not matter how wonderful any product is for your use, you MUST use a product and apply it per specifications of the OEM.

James Watts
- Navarre, Florida
December 16, 2008

James is right, but this doesn't restrict you to only those materials or processes that were pre-approved by the OEM at the time the drawing was done. If you want to use something different (perhaps something that didn't even exist at the time the drawing was done) there is no reason at all not to go to the OEM with a request that they now approve the different material or process.

Bill Reynolds
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

December 18, 2008

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