Montmorillonite as corrosion protective pigment

Different types of montmorilonites (MMTs) were studied for a survey of properties which may contribute for corrosion control, while they are employed as pigments in corrosion protective organic coatings. Experimental methodology involves epoxy novolac paints specially formulated with iron oxide plus 1 or 5 wt.% MMTs, long term corrosion tests, gravimetric tests, titrations of MMTs filtrates and suspensions. The emphasis in literature is that MMTs improve barrier properties. Nevertheless, results revealed that MMTs are not inert pigments. They have two important properties hardly considered: active corrosion inhibition and control of H+ permeation which depend on MMTs affinity by water.