Zinc tetroxychromate

Zinc tetroxychromate [13530-65-9] approximately 4ZnO ZnCrO xH20, has a somewhat lower chromate solubiUty than 2inc yellow and has been used in wash primers. 

Zinc chromate and zinc tetroxychromate have also been used successfully in anticorrosive paints. Both pigments function by releasing chromate ions which passivate the steel surface. In common with lead pigments, those... 

The standard etch primer (WP-1, DEF-1408) consists of two solutions, one containing polyvinyl butyral resin and zinc tetroxychromate in ethyl alcohol with n-butanol, and the second containing phosphoric acid and ethyl alcohol. It is essential that a small critical amount of water be present in the latter. The two solutions are mixed in appropriate ratio for use the mixture deteriorates and should be discarded when more than 8 h old. Single-pack etch primers of reasonable shelf life are available but contain less phosphoric acid than the above and are not considered to be so effective. 

The reactions which take place when the mixed etch primer is applied to a metal are complex. Part of the phosphoric acid reacts with the zinc tetroxychromate pigment to form chromic acid, zinc phospliates and zinc chromates of lower basicity. The phosphoric acid also attacks the metal surface and forms on it a thin chromate-sealed phosphate film. Chromic acid is reduced by the alcohols in the presence of phosphoric acid to form chromium phosphate and aldehydes. It is believed that part of the chromium phosphate then reacts with the resin to form an insoluble complex. Excess zinc tetroxy chromate, and perhaps some more soluble less basic zinc chromes, remain to function as normal chromate pigments, i.e. to impart chromate to water penetrating the film during exposure. Although the primer film is hard... 

Zinc chromium oxide (ZrCr04) Zinc hydroxychromate Zinc tetraoxychromate Zinc tetraoxychromate 76A Zinc tetraoxychromate 780B Zinc tetroxychromate Zinc yellow Zincro ZTO. Used as a yellow pigment in paints, varnishes, oil colors, linoleum, rubber etc. [hydrate] fine yellow powder slightly soluble in H2O. Landers-Segal Color. 

Zinc tetrachromate Zinc tetraoxychromate Zinc tetroxychromate. See... 

Zinc tetraoxychromate Zinc tetroxychromate Zinc yellow... 

Zinc chromate. See Zinc chromium oxide Zinc chromate, basic. See Zinc tetroxychromate Zinc chromate (VI) hydroxide. See inc chromate... 

Zinc tetrachromate. See Zinc chromate Zinc (II) n-tetradecanoate. See Zinc myristate Zinc tetraoxychromate. See Zinc chromate Zinc tetroxychromate CAS 49663-84-5... 

Zinc tetroxychromate. See Zinc chromate Zincum N29 Cos/Veg, Zincum N29. See Zinc stearate... 

Ammonium hexachloroplatinate H8CrOi2Zns Zinc tetroxychromate H8N2O3S... 

For zinc chromate, the inhibiting ion is CrOj, solubility relations being just right to release at least the minimum concentration of the ion (>10 mole/liter) for optimum inhibition of steel. The solubility of zinc tetroxychromate is reported to be 2 X 10 mole/liter [3]. Lead chromate, on the other hand, is not nearly... 

The action of etch primers in part involves phosphating, followed, for example, by the formation of zinc tetroxychromate/chromium phosphate layers, and a final layer of organic polymer film. A typical composite film, excellent for adhesion both to paint and to the base metal, is shown in Figure 12.14b. 

Two-pack etch primers usually contain an anti-corrosive pigment. In traditional formulations, zinc tetroxychromate was used. Current products, however, are mostly chromate-free, in response to environmental pressures. The zinc tetroxychromate has been replaced with a small amount of less toxic anti-corrosive pigments, such as zinc phosphate. Anticorrosive performance may be compromised, to a degree, by such substitutions. 

More generally, acidic depolymerization products can be leached out of many films of paint, unless suitable pigments are incorporated. Zinc dust plus zinc oxide was the original acid scavenger. Zinc phosphate, zinc ferrite, and calcium borosilicate will each exert an anodic inhibitive function at pH values exceeding 7 while zinc chromate, zinc tetroxychromate, and strontium chromate act independently of pH value (Van Eijnsbergen, 1988). In general, the pH of aqueous paint film extracts should be between 7.5 and 8.5 and certainly not below 6 or above 10. 

AP2A Two pack polyvinyl butyral (PVB) Zinc tetroxychromate 85 10 15... 

The principal chromate-based pigments are basic zinc potassium chromate (also known as zinc yellow or zinc chrome), strontium chromate, and zinc tetroxychromate. Other chromate pigments exist, such as barium chromate, barium potassium chromate. 

Zinc tetroxychromate, or basic zinc chromate, is commonly used in the manufacture of two-package polyvinyl butyryl (PVB) wash primers. These consist of phosphoric acid and zinc tetroxychromate dispersed in a solution of PVB in alcohol. These etch primers, as they are known, are used to passivate steel, galvanized steel, and aluminium surfaces, improving the adhesion of subsequent coatings. They tend to be low in solids and are applied at fairly low film thicknesses [23]. 

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