Soluble Salts, Metal Corrosion and the Osmosis Effect
Chlorides, sulfates and nitrates, also referred to as soluble or dissolved salts, react with steel to form unstable corrosion products that lead to early coating failure.
Specifically, these anions dissociate from their original salts to form stronger, electro-chemical bonds with steel. They are hygroscopic in nature and, through osmosis, react with moisture in the air. The newly-formed electrolyte in the presence of the active anodic and cathodic sites of steel are a pathway for metal corrosion.
These salts are invisible to the eye, are re-generating and require very little oxygen to form widespread corrosion. Sources for chlorides include water treatment and marine environments, while sulfates and nitrates form largely as the result of fuel emissions.
For coastal, marine environments or when painting larger assets in atmospheric conditions, residue-free low pH cleaners are recommended to remove these ionic chemical compounds.