Questions about E-Coat

Ask an Expert From: Products Finishing, from Finishing Help, LLC

Posted on: 6/5/2010

Q. Does E-Coat work on cast iron pumps and valves?

Q. I am discovering E-Coat. I have only done epoxy powder coating. Does E-Coat work on cast iron pumps and valves? Can E-Coat be approved for drinking water? D.D.

A.The simple answer to both of your questions is “yes”. However, several considerations need to be addressed due to the type of parts you are coating. Cast iron normally coats well, but “gassing” during curing can be a problem. If you are not experiencing any out gassing when curing powder, there should not be a problem with e-coat.

The major challenge for parts like yours in e-coating is what is known as “air pockets and puddles.” Air pockets are surfaces that do not get coated because air gets trapped in recessed areas and the coating cannot deposit where the air is located. If your parts do not require 100% coverage, the air pockets will probably not be a problem.

"Puddles" are likely to be more of a problem with pumps and valves. Puddles result in dragging solution from the pretreatment system into the e-coat bath and from the bath into the post rinse and cure oven. Dragin and/or dragout are major concerns in e-coating. If you are currently having to blow out liquid from parts before powder coating, puddles during electrocoating will be a problem.

The best reasons to consider e-coat for these parts are more complete coverage, better corrosion protection, and more uniform coating. Usually pumps and valves have tight tolerance dimensions that may require masking with powder coating. Since e-coat is so uniform, the coating thickness can be built into the dimensions or tolerance.

Older e-coats used to contain some heavy metals (lead, chrome, and/or tin) which might create a problem with potable water contact. Newer e-coats are totally HAPS free and will be approved for drinking water. Contact the Electrocoat Association at www.electrocoat.org to locate possible paint and equipment suppliers. These are the same people that can evaluate your parts for the potential problems discussed above.

 


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