Powder Coating to Survive 500-hour Salt Spray

Question:

I work on a project that requires 500-hour salt spray on our refrigerator cases made from steel. What coating to should I use? D.G.

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Answer:

Welcome folks to the new game show called “Select the right coating.” This game is a cross between roulette and the Wheel of Fortune. We spin the wheel and see what coating to use on our product that requires 500 hours salt spray corrosion resistance on a steel substrate. Let’s see what the answer is by spinning the wheel. Whirrrrrrrrrrrrrrrr, click, click, click…The answer is iron phosphate and polyester powder coating. Let’s try again!! Whirrrrrrrrrrrrrr, click, click, click…The answer is iron phosphate and e-coat. Let’s try again!! Whirrrrrrrrrrrr, click, click, click…The answer is iron phosphate and two-coat liquid paint. Hmmm. This is starting to look more like Russian roulette instead of “Select the right coating.” Maybe I should re-think my approach?

I know what you’re saying: “Don’t be so ridiculous, we’re smarter than that.” Well I am just trying to make a point. You can get the same performance from many combinations of pretreatments and coatings for a given substrate. In this case the substrate is steel, therefore selecting a compatible pretreatment (iron phosphate) was the easy part. The coating selection becomes the tricky part. You can get there many ways. Selecting the right coating for you may depend upon the availability of equipment. For instance, you may already have a liquid spray operation, so looking at powder coating would not make sense. Selecting the right coating for you may depend upon environmental considerations, where powder coatings have numerous benefits. There may be other coating parameters, such as mechanical toughness, that are almost as important as corrosion protection, again favoring powder coating. Coating cost is always an issue, again favoring powder coatings. Coating selection requires careful thought and consideration of all the coating and process requirements. Selecting a coating without this careful consideration will be much more like Russian roulette than you would like.