Coatings and corrosion
ISO 8501-1: Preparation of steel substrates before application of paints, visual assessment of surface cleanliness
The visual reference for how clean steel must be before painting.
01Purpose
ISO 8501-1 specifies rust grades and preparation grades of steel surfaces, assessed visually by comparison with representative photographs.
02Scope
Rust grades A to D describe the initial condition. Preparation grades include blast cleaning Sa 1, Sa 2, Sa 2½ and Sa 3, hand and power tool cleaning St 2 and St 3, and flame cleaning Fl.
03Main requirements
- Visual assessment with photographic references
- Preparation grade specified by the coating system
- Assessment without magnification
- Complementary standards for profile, dust and soluble salts
04Typical applications and industries
All painted steel. Sa 2½ is common for high performance systems.
05Audit and inspection considerations
- Is the grade checked before priming?
- Are dust and salts checked where specified?
- Is profile measured?
06Common nonconformities
- Mill scale remaining
- Flash rust before priming
- Dust on surface
- Profile outside specification
07How QUALITAS TR can support
Checked in every coating inspection.