Atmospheric Corrosion and Precipitation Runoff From Zinc and Zinc Alloys Surfaces

The long-term atmospheric corrosion performance of rolled zinc and three thermal-sprayed (TS) zinc materials (Zn, Zn-15Al, and Al-12Zn-0.2In) was characterized by measuring corrosion product concentrations in precipitation runoff at coastal marine and inland sites. Corrosion rates and average zinc concentrations in the runoff were greater at the site having higher annual rainfall. Higher chloride concentrations did not seem to affect either the corrosion rates or the zinc concentrations in the runoff at the coastal site compared to those of the inland site. Zinc runoff concentrations were higher for TS Zn than rolled zinc due to the greater surface area of the thermal-sprayed surface. Average cumulative zinc runoff losses for the two sites were: 64 {micro}mol Zn/L for TS Zn, 37 {micro}mol Zn/L for rolled Zn, 24 {micro}mol Zn/L for TS Zn-15Al, and 1.8 {micro}mol Zn/L for TS Al-12Zn-0.2In. Cumulative zinc runoff losses were directly related both to the precipitation rate and to the availability of Zn in metal surfaces, a consequence of surface roughness and surface chemistry properties of the metal