Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

March, 2009

Primer Preparation

Q. I am sandblasting a large mild steel sculpture that was commissioned, and it will be primed with an epoxy primer and then top coated with an acrylic. The steel is quite clean, nearly mill, and the stainless welds have been ground smooth. The sandblasting is very slow over the approx. 200 square feet of material, and I can't do it in less than two days. I am in a dry, heated, stable environment. I am worried that it might start to oxidize before I apply the primer, which perhaps will eventually eat through the paint. Since the steel is new, could I sandblast quickly and less thoroughly? If I go slowly, take two days, and get down to fresh metal everywhere, is it likely to rust? Would it be better to use a sander instead of blasting? Thank you for the opportunity to ask-

A. If you live in a dry stable environment you should not expect any corrosion to take place during the two days it takes to blast the steel. I certainly would prefer blasting than sanding because the former will do a better job of removing the any oxides that are currently present, and blasting will provide the steel with a profile. Where will there sculpture be exposed once it has been coated?You should not be concerned about minor oxidation of the steel, but you should be concerned if there is moisture and the steel starts to rust. To further prevent the formation of rust, you can consider covering the statue overnight with a piece of plastic sheeting.

From your email I'm not sure if you are expressing concern that oxidation will eat through the paint? If so, be assured that it won't. But if the coated statue will be located in a very humid environment, moisture and oxygen can migrate through the epoxy+acrylic system and start the corrosion process. If the statue will be located in a relatively dry environment I don't think you need to worry.


Ron Joseph

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