Zinc-containing pigments

Etch primers are widely used. They are mostly based on polyvinyl butyral and contain chromates and phosphoric acid. They are said to act both as primers and as etching solutions because it is believed that the chromates and phosphoric acid form an inorganic him, which provides adhesion, while oxidised polyvinyl butyral provides an organic him. For direct application to new galvanised steel, the best known primers are based on calcium orthoplumbate pigment and metallic lead, but these are now less used for environmental reasons. Zinc-dust paints and zinc-phosphate pigmented paints are also used, but the trend is to use pretreatments to assure good adhesion. 

The most important phosphate-containing pigments are zinc phosphate [5.67]-[5.69], [5.71] basic zinc phosphate [5.70], [5.71] chromium phosphate [5.72] aluminum triphosphate [5.73] barium phosphate [5.53] aluminum zinc phosphate [5.68] and zinc/iron phosphate [5.71], Phosphate ions form protective coatings of basic iron(III) phosphate on an iron surface. Their composition is described in [5.64]. 

The most important phosphate-containing pigment is zinc phosphate [7779-90-0], Zn3(P04)2-4 H20, Mr 458.1. It can be used with a large number of binders (see Table 39) and has a very wide range of uses [5.67], [5.68], [5.70], [5.71], [5.82], Zinc phosphate is usually produced on an industrial scale from zinc oxide and phosphoric acid, or from zinc salts and phosphates [5.83], Composition and properties are given in Table 40. 

Zinc-Containing Chromate Pigments. Zinc chromate is produced by reacting an... 

Fig. 9. Principle of the corrosion inhibiting mechanism of the epoxy-acrylate-silane superprimer containing the zinc phosphate pigments, which protect the metal on-demand [30].

Coating containing a zinc powder pigment in an inorganic vehicle. 

A paint containing zinc powder pigment and an organic (containing carbon) resin. 

Where cations such as lanthanides, zinc and calcium are able to be released, they have demonstrated an ability to inhibit corrosion. Bohm et al. [139] examined the release of Ce and Ca from bentonite pigments they showed that the calcium-exchanged pigment matched the anti-delamination performance of a strontium chromate containing control, and the cerium containing pigment provided superior anti-delamination performance compared to the chromate containing system. 

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