Seawater typically contains 1-25% salinity, with an average value of 3.5% commonly used for calculations. It contains substantial concentrations of dissolved oxygen, nitrogen, and carbon dioxide, which collectively accelerate zinc corrosion. Chloride ions (accounting for approximately 55% of total ions) inhibit protective film formation and promote corrosion, while magnesium and calcium ions facilitate the creation of insoluble salts on the zinc surface, encouraging protective film development and gradually reducing corrosion rates.
The corrosion products of zinc in seawater include carbonates, hydroxides, and chlorides. The corrosion rate of zinc coatings in marine environments generally ranges from 50 to 650 mg/dm²·year.
