Powder Coating Over 304-SS Tubing

Question:

I want to powder coat over 304 stainless steel tubing. What steps should I consider for surface preparation to get the best adhesion? Are there any special types of powder coating that I should consider? L.H.

Answer:

Surface preparation is more important than coating selection when powder coating stainless steel. That is because adhesion of the powder coating to the substrate is of primary concern, since the powder coating does not add any other value to stainless steel, other than color.

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The recommended pretreatments for stainless steel are as follows:

• Wash the surface using an alkaline cleaner to remove all organic soils
• Provide “tooth” on the surface for the coating to “bite” onto. This can be accomplished using mechanical means (i.e. wire brushing, sanding, grit blasting, etc.) or chemically using an adhesion promoter from the glass industry called Silane.

As for using special powders, any powder coating will work on stainless steel, once you prepare the surface. The only differences are the coating properties. So select the powder coating that has the properties you need (see previous question). Be sure to consider UV stability if outdoor exposure is important, flexibility if you plan on bending the tubing after coating, hardness if you have abrasion issues, etc.