Evaluation of the anticorrosive properties of environmental friendly inorganic corrosion inhibitors pigments

Anticorrosive properties of the following environmental friendly inorganic pigments were evaluated: zinc phosphate (ZP), zinc molybdate (ZM), zinc calcium molybdate (ZCM), zinc phosphomolybdate (ZPM) and zinc calcium phosphomolybdate (ZCPM). AISI 1010 steel samples were immersed in 10-2 mol dm-3 NaCl aqueous solution saturated with one of the pigments, followed by mass loss measurements, by monitoring the open circuit potential with immersion time and by potentiodynamic linear polarization at 1 mV s-1. The corrosion products on the steel surface were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray and X-rays Diffraction analyses. All the pigments inhibited the corrosion of steel. The films formed on the steel surface protect the substrate against corrosion. The results suggest a synergic effect of phosphate and molybdate compounds in the phosphomolybdate-based pigments, improving the corrosion resistance of steel. The ZMP and ZCPM decreased the corrosion rate by a factor of 2.15 and 3.50, respectively