Surface Preparation for Nuclear Coating Systems
Cleanliness is a measured condition
Surface preparation removes contaminants that impair adhesion or later cause corrosion or stress-corrosion cracking. Abrasive blasting to near-white metal (SSPC-SP 10/NACE No. 2) is common for immersion or high-performance systems; commercial blast (SP 6) or power-tool cleaning (SP 3) may be allowed only where the specification permits. Abrasive must be clean and chloride-free; recycled abrasive can carry salts. Soluble salts are measured, commonly with a Bresle patch and conductivity meter. Oil, grease, dust, weld spatter, laminations, and sharp edges must be addressed. Surface profile must be angular and within the product range; excessive profile can cause thin spots or pinholes.
Traps include assuming blasting removes all salts, creating too deep a profile, skipping testing after blasting, and ignoring humidity or flash rust.
Rule of thumb: prepare, test, and protect. If soluble salt conductivity exceeds the project limit, re-clean and retest; do not paint over it.
Worked example: After SP 10 blasting, a Bresle test reads above the specified limit. Re-clean the area and retest before priming; a tie coat does not seal in the salt.