Preparing Steel Before Painting: A Practical Guide

Preparing steel for painting is a sequence, and skipping any step in it undermines everything applied afterwards.

First, degrease. Oil and grease are not removed by blasting — they are driven into the surface. Clean with a suitable detergent or solvent before any abrasive touches the steel.

Second, deal with the fabrication. Sharp edges should be radiused, weld spatter removed and slag chipped off, because coatings thin dramatically over sharp arrises and fail there first.

Third, blast to the specified grade — usually Sa 2½ under ISO 8501-1 — with the abrasive sized to produce the profile stated in the coating datasheet, typically 50–75 microns.

Fourth, check conditions and prime. Steel temperature must be at least 3°C above dew point, and the primer should go on the same day, before flash rusting begins. On coastal steelwork, test for soluble salts and wash if required.

Rayco handles the blasting stage and coordinates with your coating contractor so the primer goes on inside the window.