Spinels – reactive pigments affecting the diffusion of corrosive substances through the coatings

Abstract

Studies the spinel pigments containing Zn, Ca, and Mg cations from the point of view of reactivity with corrosive substances of acidic nature, which diffuse through the coating at activated corrosion. Proposes the mechanisms of anticorrosive activities of these pigments in an epoxy resin based binder, showing a high chemical stability. A microscopy method was used for following the diffusion of corrosive acidic substances through the film.

Investigation of the anticorrosion efficiency of ferrites Mg1−xZnxFe2O4 with different particle morphology and chemical composition in epoxy-ester resin-based coatings

“…The method of following the corrosion losses in the suspensions of organic coatings containing spinels gives evidence on the Table 4 Relative corrosion-induced weight losses of steel panels submerged in aqueous extracts of the pigments (Xp) and of the paint films (X f ), and pH and specific electric conductivity ( ) levels of the extracts. possible reactions inside the coating, namely that yet in the liquid state, on the formation of film and partially also on ageing the film already in the hardened state [27]. In an epoxy ester resin binder, the acidic COOH binder groups are present, except the hydroxyl groups.…”

Acid-resistant organic coatings for the chemical industry: a review

“…Reactive pigments work by partly reacting with, thus removing, and blocking the permeating substance [100,107]. A combination of reactive and inert pigments is claimed to reduce the diusion of aggressive species through a coating to a greater degree, than if used individually [104].…”

Anti‐Corrosive Properties and Physical Resistance of Alkyd Resin–Based Coatings Containing Mg‐Zn‐Fe Spinels

“…Mixed oxides in the spinel form, particularly ferrites containing Ca, Zn, Mg and their solid solutions, applied in paints already assume a firm position in anti-corrosion protection of metals [10,11]. More efficient than the spinel-structure ferritetype pigments with a combination of two cations in the lattice structure (ZnFe 2 O 4 , MgFe 2 O 4 ) are second-generation spinel pigments with three cations (Mg 1-x Zn x Fe 2 O 4 and Ca 1-x Zn x Fe 2 O 4 ) [12]. Ferrite pigments are reactive particles on the surface in which there occur chemical reactions leading to the formation of less aggressive substances and a protective film during the diffusion of the corrosion substances through the polymeric film [13].…”