Coating for Aluminum

Ask an Expert From: Products Finishing, ,

Posted on: 4/1/2004

Question: I have the same situation as the fellow who asked the question in the January 2004, Painting Clinic (see "Repainting Aluminum coatings"). However, I am a bit more lost.

Question:

I have the same situation as the fellow who asked the question in the January 2004, Painting Clinic (see "Repainting Aluminum coatings"). However, I am a bit more lost. In your answer you mentioned, “This leaves you with the choice between two-component polyurethanes and polyesters. Either choice is durable and available in a wide range of colors and glosses.” What exactly are two-component polyurethanes and polyesters? Can I get it from one of the “Big Box” hardware stores? And last but not least, is it a complex process? C.R.

Answer:

In the January 2004, Painting Clinic, W. T. wanted to repaint aluminum castings. I recommended using an epoxy primer topcoated with a polyurethane. I did not mention polyesters. But since you asked, you can buy two-component polyurethane paints and polyester paints, which are two different chemistries, from paint stores. They used to be strictly industrial products, but are now available as trade sales products.

A discussion of the chemistries of polyurethane, epoxy and polyester paints is well beyond the scope of the Painting Clinic. However, I can tell you that the components are packaged in separate containers. They are mixed prior to use in specified proportions. They must be applied within a specified time period, because they react and solidify after the two components are combined and are unusable thereafter. Any residual paint must be removed from the painting equipment before it solidifies. Other than that, it is not a complex process and is done all the time in commercial and industrial applications.



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