We have a customer who wants to electrocoat stainless steel parts (grade 430 or 436). We have a complete pretreatment system for use prior to electrocoat. We are presently coating steel and aluminum in our electrocoating system but have never handled stainless steel. This job presents an excellent opportunity for us. Can we expect adhesion problems with normal pre-clean treatments? What other options are available to coat stainless steel? R.W.
The reactions that occur at the substrate-coating interface during electrocoating provide maximum adhesion of the coating to the substrate. Therefore, I would not expect adhesion problems of electrocoat to stainless steel with normal pretreatments designed for the electrocoat process. However, if there is a problem, you have another option. Sometimes stainless steel requires special pretreatments to promote adhesion. For this reason, stainless steel is pretreated using surface abrasion and phosphoric acid activated vinyl wash primers. You cannot use the wash primer, but you can abrade the surface. Light abrasive brushing, sanding or surface blasting will roughen the surface and promote adhesion. It is important to note that this abrasion is in addition to the normal pretreatment prior to electrocoat.