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Does Galvanized Iron sheet require pretreatment?

December 29, 2009

Sir,

I am working with one of biggest groups in india. We are in the manufacturing of modular office funiture. I want to start with GI sheet instead of CRCA MS sheet . Is pretreatment for GI sheet really required ? We have nano technology pretreatment with multimetal line option. Is degreasing alone sufficent for GI? My final application is powder coating. Please suggest.

Regards,

Jayant Joshi

Jayant Joshi
powder coating incharge - Aurangabad, Maharashtra, India

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Mr. Joshi,
If someone answers yes, degreasing is enough, would you go into full scale production? I don't mean to offend anyone with this response but you really should run some samples of all of the pretreatment and substrate options available to you and then make a decision based on the results of some kind of testing done to those samples. The minimum accepted form of testing would be to have the panels salt spray tested. The pretreatment/substrate combo that comes back with the best results should be the process used.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
December 29, 2009

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Thanks, Sheldon, that is an excellent point. You don't want to go into production based on a theory or a guess that something will work :-(

But if someone answers no (and I guess I'm doing that), suggesting that the powder coating will not properly adhere to a galvanized surface that has been simply degreased, it may be advisable to do an adhesion test as well. There is a good chance that the nanoparticle multimetal pretreatment will be okay, Jayant, after testing as Sheldon suggests, but be very careful about assuming the degreasing worked unless the testing is pretty extensive.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 30, 2009

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All zinc or zinc coated metals require pretreatment for good adhesion.

Plenty of applicators do no pretreatment, and the difference is undetectable until after about 4 weeks.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

December 30, 2009

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December 30, 2009

Every sheet or roll of metal will have different amounts of dirt or corrosion and who knows what on them, so there is no universal answer.
Also solutions work better when they are new. How well will they work on the last set of parts before you dump the tank?

Lots and lots of variables, with no constant answer.

That is what pilot lines and testing are for.

James Watts
- Navarre, Florida