The present study deals with the investigation of the effects of partial replacement of sacrificial zinc dust by high efficiency barrier micaceous iron oxide (MIO) pigments on the corrosion protection behaviour of inorganic zinc rich coatings. To this end, waterborne zinc rich silicate paints based on nanosilica modified potassium silicate were formulated with different contents of zinc and MIO. After being applied on carbon steel panels, the coatings were evaluated by electrochemical impedance spectroscopy, corrosion potential measurements and salt spray test. Replacement of zinc by MIO in the formulation of zinc rich paints was revealed to shorten the duration of cathodic protection stage while on the other hand giving satisfactory results in 1000 h of salt spray test. It was concluded that the incorporation of MIO pigments in conjunction with zinc into the formulation of inorganic zinc rich coatings is a potential means to control the reactivity and the barrier protection stage.
PurposeThe aim of this paper is to study the corrosion protection behavior of water‐borne inorganic zinc‐rich coatings based on potassium silicate/nanosilica developed with various zinc and micaceous iron oxide (MIO) contents during cathodic protection stage.Design/methodology/approachThe formulated coatings were applied on carbon steel panels and were subjected to electrochemical impedance spectroscopy (EIS) and free corrosion potential measurements for characterization of corrosion protection behavior. Also atomic force microscopy (AFM) and optical microscopy were used to investigate the surface topography of coatings.FindingsAll of the coatings preserved the cathodic protection ability throughout 75 days of exposure to 3.5% NaCl solution. Supporting results of electrochemical tests and microscopic observations revealed that replacement of zinc by MIO particles reduced both the rate of reactivity and the duration of cathodic protection of inorganic zinc‐rich coatings. It was observed that the coatings demonstrated a reactivation step after a dry‐wet cycle implying that cyclic immersion can change the overall duration of cathodic protection stage.Originality/valueThe paper describes formulation and investigation of corrosion protection behavior of an environmentally friendly zero‐VOC coating as well as providing an insight into EIS of zinc‐rich coatings.
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