Ask the Expert Question-and-Answer Archive

by Ron Joseph

January , 2008

Scratch Resistant Surface

Q: We manufacture a machine that I would like a strong scratch resistant finish. The machine will be installed indoors and is fabricated of both black iron sheets as well as galvanized paint grip metal. Should I be concerned about the metal pre-treatment prior to finish as well as the final finish coat.

A: You should always be concerned about pretreatment. This applies especially to the galvanized steel, because some paints do not adhere well to untreated zinc. I am working on a case in which paint was applied to pretreated galvanized sheeting several weeks after the pretreatment had been applied. In this case large areas of paint peeled off and fell to the floor.  

The degree of surface preparation that you should specify is largely based on the type of exposure the machine will experience and the type of coatings that will be applied.  If the cohesive strength within the coating is greater than the adhesive strength between the coating and the substrate (steel or galvanizing) the paint might pop off and you might experience serious delamination. 

Regards,

Ron Joseph