Chromium oxide pigment

Chromium oxide green Pigment Green 17 formula Cr Oj 

Hydrated chromium oxide green Pigment Green 18 formula Cr203-2H20 

---

Uses. The most important areas of use of pigments are paints, varnishes, plastics, artists colors, printing inks for paper and textiles, leather decoration, building materials (cement, renderings, concrete bricks and tiles—mostly based on iron oxide and chromium oxide pigments), leather imitates, floor coverings, rubber, paper, cosmetics, ceramic glazes, and enamels. 

Oxides and oxide -hydroxides Iron oxide pigments Chromium oxide pigments Mixed metal oxide pigments chromium oxide cob chromium oxide hydrate green alt green and b lue iron oxide red iron oxide orange chromium rutile orange iron oxide yellow nickel rutile yellow, chromium rutile yellow iron oxide brown zinc iron spinell, Mn-Fe-brown... 

Chromium(III) oxide crystallizes in the rhombohedral structure of the corundum type space group D3d-R3c, Q 5.2 g/cm3. Because of its high hardness (ca. 9 on the Mohs scale) the abrasive properties of the pigment must be taken into account in certain applications [3.44], It melts at 2435 °C but starts to evaporate at 2000 °C. Depending on the manufacturing conditions, the particle sizes of chromium oxide pigments are in the range 0.1-3 pm with mean values of 0.3-0.6 pm. Most of the particles are isometric. Coarser chromium oxides are produced for special applications, e.g., for applications in the refractory area. 

The workup is then carried out as described above. A chromium oxide pigment obtained by this process typically contains (wt%) ... 

Process wastewater may contain small amounts of unreacted chromates recovery is uneconomical. Prior to release into drainage systems, the chromates in these wastewater streams must be reduced (e.g., with S02 or NaHSOj) and precipitated as chromium hydroxide [3.60]. In Germany, for example, the minimum requirements for wastewater in the production of chromium oxide pigments are specified in [3.61]. 

International, technical specifications for chromium oxide pigments are defined in ISO 4621 (1986), they must have a minimum Cr2Oa content of 96 wt%. 

Change in Strength (see ease of dispersion and PVC) Chemical resistance Chlorides, water-soluble (see matter soluble) Chromium oxide pigments 2812-1 ISO 2812-1 EN ISO 2812-1... 

Chromium oxide pigments chromium oxide chromium oxide hydrate green ... 

Case study HDPE-based roof slates (another main components were a flame retardant and an inorganic filler) made with an insufficient amount of both green chromium oxide pigment and a UV stabilizer after about 2 years on a roof in a southern state severely faded (L on the Hunter Lab units scale went from the initial 46 to 64 units). Inspection of their surface under a light microscope revealed a vast net of cracks (Fig. 15.16) compared with an unexposed tile (Fig. 15.17). A 10 times higher magnification shows cracks in more detail (Fig. 15.18). 

According to Heaton (1928), academy blue was a compound colour said to be based on ultramarine (presumably the S3mthetic form) and the hydrated chromium oxide pigment viridian iqq.v.). 

This is a grey-black or black copper compound with composition CuCt204 (also termed cupric chromite). It is also a component in a brown-black or black copper-chromium oxide pigment mentioned in the pigment hterature and said to be a mixture of CuCr204 and CuO. 

---