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Zirconium phosphate in mild steel pretreatment systems

September 10, 2009

We have a standard 4 stage iron phosphate pretreatment process followed by epoxy polyester coating line.
I'm very interested in changing to a Zirconium phosphating system to drastically reduce the energy, water, effluent costs.
I have a mild steel pretreatment tunnel and I have just heard that Zirconium will eat it for lunch..... Is this true and if so is there any way of stopping the mild steel from being eaten.

Any feedback would be very useful,


Thanks,

Simon S [last name deleted for privacy by Editor]
Engineering Manager - painting process - Milton Keynes, Bucks, England

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Hi Simon,

The easiest solution may be to drop a plastic liner in the tank that will contain the phosphating bath.

George Gorecki
- Naperville, Illinois
September 11, 2009

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You do not mention what metal you are processing through your plant... but I guess it must be aluminium. Unfortunately, I have very little experience with zirconium phosphate plants... however, did come across it a few months ago. This potential client was coating aluminium window shelves and occasionally also put some mild steel components through.
The problem was, the mild steel items came out of the spray chamber with flash rusting. I asked the pretreatment supplier why this happened and apparently this client was informed he could mix the metals in the pretreatment but at a much lower ratio than they were that day. It seems that this zirconium phosphate runs at a pH of 2.0 (very acid) and mild steel, as we all know, hates acid environments. Maybe there are other proprietary brands that overcome the restrictions of Al items only... I would be interested to know.

Terry Hickling
Birmingham, United Kingdom
September 15, 2009