Painting Stainless Steel Flexible Tubing

Q. I am looking for a method to paint stainless steel flexible tubing for gas and water lines. We have made a few attempts to paint them, and on the surface, they look flawlessly painted, however, since the tubing (which is around 1/2 inch in diameter) is flexible stainless steel, every time we bend it, say a 90-degree angle, it makes a cracking noise, which is most likely the paint cracking from the bending. What methods/processes are there to have this not occur, and what paint is necessary? W. S.

 

A. You may have two problems here: paint adhesion and paint flexibility. Paint adhesion to stainless steel can be enhanced by using pretreatments such as acid etching, abrasion. It is important to note that the first step in any pretreatment is surface degreasing. Acid etches must always be used under controlled conditions. A safer pretreatment is to abrade the surface. This can be done by sanding, wire brushing or media blasting. Phosphoric acid activated vinyl wash primers are also used as pretreatments. After degreasing and pretreatment, apply the organic coating as soon as possible.

The other problem is paint flexibility. To solve this problem, you must use a flexible paint. Elastomeric coatings have a better chance of flexing without cracking. You should consider using vinyl plastisols, organisols and certain flexible polyurethanes. In some cases, primers must be used with these coatings. The vinyl wash primer may be used for this purpose.