04/16/2026
How Abrasive Blasting Works β Red Seal Exam Breakdown
If you're preparing for your Red Seal Industrial Painter & Decorator exam, you need to understand the complete abrasive blasting process. This is one of the most heavily tested topics.
Here's the process step by step:
1. Environmental Check
Before blasting, measure ambient temperature, relative humidity, and dew point. Steel surface temperature must be minimum 3Β°C above the dew point. If moisture is present on the surface, do not blast. Flash rust will form immediately on exposed steel.
2. Abrasive Media Selection
Media is selected based on the required anchor profile from the coating manufacturer's data sheet:
β Steel grit β angular, recyclable, 2-4 mil profile
β Garnet β low dust, 1.5-3 mil profile
β Coal slag β economical, single use
β Aluminum oxide β hardest media, finest profile control
3. Blast Technique
Hold nozzle 12-18 inches from surface. Maintain 80-90 degree angle for maximum cleaning. Use consistent overlapping passes. Nozzle pressure typically 90-110 PSI.
4. SSPC Cleanliness Standards
β SP 5 / NACE 1 β White Metal, 100% clean
β SP 10 / NACE 2 β Near-White, 95% clean
β SP 6 / NACE 3 β Commercial, 67% clean
β SP 7 / NACE 4 β Brush-Off, loose material only
5. Anchor Profile Measurement
Measured using Testex replica tape and spring micrometer. Typical spec for epoxy primers is 1.5-3.0 mils.
6. Prime Within Time Window
Apply primer as soon as possible after blasting. In high humidity, flash rust can form within 1-2 hours.
Know this process inside out. The exam will test every part of it.