Powder vs. E-coat

Ask an Expert From: Products Finishing, , from Powder Coating Consultants, Div. of Ninan, Inc.

Posted on: 5/1/2004

Question: The statements regarding e-coat and powder coating caught my interest as we have done considerable testing in this regard.

Question:

The statements regarding e-coat and powder coating caught my interest as we have done considerable testing in this regard. These two types of engineered coatings are quite different so comparing them tends to highlight their individual limitations. While it is true that some epoxy powder coats have a significantly higher molecular weight than the conventional cathodic epoxy electrocoats, the electrocoat primers are much more efficient at low-film builds (low cost). An epoxy electrocoat at 0.8 mil is a great primer...try to apply an epoxy powder at that film thickness and you will have a serious problem with holidays. The high-molecular weight of some epoxy powders, however, provides extraordinary chip resistance. In many applications chip resistance, not corrosion resistance, is more important (but you get improved corrosion resistance with the higher-molecular weight resins by default).

The greatest distinction between these two technologies is mode of application. The immersion process with e-coat will cover those IDs in the tubes and channels (provided, of course, there is no air pocket to restrict coverage). The powder coat processes are still line-of-sight with some electrostatic wrap. The biggest problem with Army equipment is lack of paint coverage, not paint type. We would never approve a conversion from e-coat to powder if surfaces requiring an immersion system were required.

Should you not have to deal with covering internal surfaces, the entire relationship changes. With the minor capital equipment costs of powder application equipment compared to e-coat, it is definitely the product of choice for small business. Transfer efficiencies of reclaimed powder are comparable to e-coat. We have epoxy powder primers at 2-4 mils that significantly outperform e-coat. Some are rated at “15-year performance” with the GM 9540P protocol; by comparison we only get 6.6 years with black epoxy/urethane cathodic e-coat using the same benchmark. If you have relatively accessible surfaces and want exceptional chip, chemical  and corrosion resistance, epoxy powder coat is the way to go!

Of course both of these technologies are vastly superior to any “wet primer” in most regards. G.S.

Answer:

Thanks for your comments. You are right that both these technologies are very different. In fact, I told the original questioner that it was like “comparing apples to oranges.” Next thing you know I’m defending the virtue of powder coating. Thanks for bringing us back to a reasonable point.

 



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