Most steel in service has already been painted, so a large share of maintenance work means putting a new coating over an old one. Overcoating comes with one rule: the new coating is only as good as the old coating's adhesion to the steel. Why it can go wrong The new coat bonds to the old coat. If the old coat is chalked, loose or barely holding on, the new coat adds weight and stress to a system that is already failing. A strong new coating also shrinks as it cures and can pu

A secondary containment area is the concrete basin around a chemical tank. It can sit empty for years, then one day it has to hold something aggressive for as long as cleanup takes. That is an unusual job for a coating, and it has to be specified in reverse. Start with the chemical, not the concrete Most coating decisions begin with the substrate. Containment begins with what is stored: What is the chemical? At what concentration? At what temperature? How long could it sit be

Two abrasive blast standards appear in most steel coating specifications: SSPC-SP 6 (Commercial Blast Cleaning) and SSPC-SP 10 (Near-White Metal Blast Cleaning). The names are close. The results are not. What they share Both remove all visible rust, mill scale, old paint and dirt. Where they differ The difference is how much staining may remain. Staining means the light shadows and streaks of rust or old coating left in the profile after blasting. SP 6: staining allowed on up

Steel blasted to a clean SSPC-SP 10, profile on target, primed the same day. Two years later the lining is covered in blisters. The inspection report never tested for the thing that caused the failure. What soluble salts are Soluble salts, mostly chlorides and sulfates, arrive on sea air, road salt, process chemicals and old rust. They cannot be seen, and they survive abrasive blasting. The blast can even drive some of them deeper into the pits. Under a coating, a small amoun