Cobalt Chromium Aluminates

Like the cobalt aluminates, cobalt chromium aluminates have excellent heat stability and weatherfastness. In many cases they have significantly better UV opacity than the Pigment Blue 28 grades. 

Regulated Colorants That Are FDA Approved. It often seems a contradiction that many of the colorants that are suitable for use in food contact applications must also appear on an MSDS as a reportable or hazardous material. Examples include zinc oxide and zinc sulfide, both zinc compounds chromium oxide green (pigment green 17), a chromium compound carbon black and cobalt aluminate blue (pigment blue 28), which is not only reportable because of its cobalt content but is also a suspected carcinogen. 

The effect of H2S concentration on total corrosion of selected alloys in 1000 hr at 1800°F is illustrated in Fig. 2. A variety of different oxidation-corrosion behaviors were observed. Ferritic alloys, like AISI 446, generally showed increased corrosion rate with decreasing H2S concentration, whereas 300 series austenitics typified by AISI 310 generally exhibited maxima at both 0.1 and 1.0 v/o H2S. IN-800 had high corrosion only above 0.5 v/o H2S. Aluminized AISI 310 and IN-800, IN-671, and several high-chromium alloys did not indicate a strong dependence of H2S concentration in 1000 hr total corrosion. Cobalt-base alloys also generally performed as shown for the aluminized AISI 310 and IN-671 specimen. 

Inorganic colorants listed in 21CFR 178.3297 include aluminum, aluminum hydrate, potassium silicate, aluminum silicate, barium sulfate, bentonite, calcium carbonate, calcium silicate, calcium sulfate, carbon black (channel process, prepared by the impingement process from stripped natural gas), chromium oxide green Cr203, cobalt aluminate (with restrictions), diatomaceous earth, iron oxides, kaolin (modified for use in olefin polymers in amounts up to 40%), magnesium oxides, magnesium silicate (talc), sienna, silica, titanium dioxide, titanium dioxide-barium sulfate, ultramarines, zinc carbonate (limited use), zinc chromate (less than 10%), zinc oxide (limited use), and zinc sulfide (less than 10%). 

Also included here are the secondary oxides (aluminates) calcium aluminate (CaAl204), cobalt aluminate (C0AI2O4), lead aluminate (PbAl204) and hercynite (iron aluminate, Fe Al204). Calcium aluminate (calciiun aluminium oxide) may be a component of the pigment known as Satin white. Cobalt aluminate (cobalt aluminium oxide) is the pigment Cobalt blue. Lead alu-minate is listed by the Colour Index (1971) under Cl 77585. Hercynite has been identified on Minoan painted pottery by Stos-Fertner et al. (1979). Chromium aluminium cobalt oxide is Turkish Green. 

The pigments used for the production of decorations generally consist of colored frits or stain mixtures crystallized in a vitreous silico-aluminous phase. The main products used as coloring are oxides of antimoity, chromium, copper, cobalt, iron, manganese, nickel, praseodymium, selenium, titanium, uranium, and vanadium [HAB 85]. 

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