Evaluating Novel Inhibitor Pigment Blends using Electrochemical Scanning Techniques (EIS, SVET and SKP)

Abstract

Abstract

One of the main applications coming to the fore for scanning vibrating electrode technique (SVET) and scanning Kelvin probe (SKP) systems is ability to look at inhibitor combinations, which could be used to replace chromates in coil-coated galvanized steels. The results are very promising using the SVET system and results with the SKP system also show results to be comparable with the SVET system. Electrochemical impedance spectroscopy (EIS) is also used to understand the mechanism of inhibition by mixture of pigments. The more promising pigment combination involves mixture of phosphates and calcium ion-exchange pigments for inhibition of corrosion on organic-coated galvanized steel. This paper presents work on a detailed study of the mechanisms of action of this mixture which has been established as effective in cut-edge and zinc inhibition. The use of the blend of inhibitors is shown to result in the development of an adsorbed phosphate film on the metal which plays an important role in the development of anodic and cathodic inhibitive control. Zinc ions also appear to have an important synergistic effect on the film composition and structure increasing its coherence and decreasing its porosity. The data confirm the anticorrosion efficiency of the pigment blend dispersed in organic coating on galvanized steel.

Keywords: inhibitors, EIS, SVET, SKP, pigments, chromates, molybdates, phosphates, calcium ion-exchange silica