Letter 11031

Phosphating and corrosion resistance 

I would to ask some question on Phosphating process. As we know the phosphating process can improve the corrosion resistance of the parts. Our company's sub-contractor produced some rust parts with phosphating. Would you tell me what the paramaters are to make sure the corrosion resistance of the finished parts. Thank you very much!

Ricky Au
- Hong Kong

Ricky,

Phosphated material alone is not a very good corrosion resistant finish. It is a very good base for powder coating and then you will get better corrosion resistant rating. If you want corrosion resistance there are different chromates on the market that will definitely be better for corrosion resistance.

Lee Moss
- Calgary, Alberta, Canada

Phosphatization layer gives good protection against corrosion while being base for oiling or coating. Otherwise protection and self healing is limited. Beware especially from excess of 'white beard' which is essentially corrosion. Of course no rust should appear before oiling/painting

Arik Lin
- Israel

You don't specify what type of phosphate. If it is iron phosphate, it should have a "sealer", either chrome or non-chrome. If it is iron phosphate, the parts should be painted or e-coated within 24 hours.

Bill Hemp
- Grand Rapids, MI

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