Slide 003: Surface Preparation Standards and Quality Control¶
Slide Visual¶
Slide Overview¶
This slide covers industry-standard surface preparation specifications, how to measure and verify blast profiles, and quality control procedures used in professional and makerspace settings.
Instruction Notes¶
Industry Standards for Surface Cleanliness¶
The Society for Protective Coatings (SSPC) and the Swedish Standards Institute (ISO 8501) define surface preparation grades:
| SSPC Standard | ISO Equivalent | Description | Appearance |
|---|---|---|---|
| SP 5 (White Metal) | Sa 3 | Complete removal of all contaminants | Uniform metallic color |
| SP 10 (Near-White) | Sa 2.5 | 95% removal of all contaminants | Slight staining permitted |
| SP 6 (Commercial) | Sa 2 | 67% removal of contaminants | Light shadows acceptable |
| SP 7 (Brush-Off) | Sa 1 | Remove loose material only | Tight rust may remain |
For most makerspace coating applications, SP 6 (Commercial Blast) provides adequate adhesion at reasonable cost and time.
Measuring Surface Profile¶
Surface profile (anchor pattern) is measured using: - Replica tape (Testex Press-O-Film): Most common field method. Place tape on surface, compress with burnishing tool, measure with spring micrometer. Accuracy: ±0.1 mil. - Digital profile gauges: Electronic stylus measures peak-to-valley depth. Models like the Elcometer 224 provide readings in 0.1 μm increments. - Comparator panels: Visual/tactile standards (SSPC-VIS 1) for quick field comparison.
Profile Depth Requirements¶
Coating manufacturers specify minimum and maximum profile depths: - Primers: Typically require 1.0–3.0 mil (25–75 μm) profile - Powder coating: 1.5–3.0 mil (38–75 μm) profile - Thermal spray: 3.0–5.0 mil (75–125 μm) profile - Adhesive bonding: 1.0–2.0 mil (25–50 μm) profile
Quality Control Checklist¶
Before applying any coating after blasting: 1. Verify cleanliness grade against specification (visual comparison) 2. Measure profile depth at minimum 3 locations per panel 3. Check for embedded contaminants (oil, moisture, media fragments) 4. Verify ambient conditions: surface temperature >5°F above dew point, relative humidity <85% 5. Apply coating within 4–8 hours of blasting to prevent flash rust on ferrous metals
Common Defects¶
- Under-blasting: Insufficient profile leads to coating delamination
- Over-blasting: Excessive profile wastes media and can thin substrate
- Embedded media: Trapped particles cause coating blisters
- Flash rust: Humidity-induced oxidation on freshly blasted steel
Key Talking Points¶
- Surface preparation is responsible for 80% of coating failures when done incorrectly
- Always verify profile depth matches coating manufacturer requirements
- Time between blasting and coating is critical — flash rust begins within hours
- Document your quality control checks for every project
Learning Objectives (Concept Check)¶
- Identify the four SSPC cleanliness standards and their applications
- Demonstrate how to measure surface profile using replica tape
- List the five quality control checks required before coating application
Last Updated: 2026-03-19