11103-86-9

Usage

Uses

Used in Anticorrosive Applications:
Potassium hydroxyoctaoxodizincatedichromate (1-) is used as an anticorrosive agent in the formulation of coatings and primers. It is effective in inhibiting corrosion and rust, particularly galvanic couple corrosion, which involves electron exchange between different metals. Even when present in low concentrations, it has the unique ability to actively suppress electron transfer at both cathodic and anodic sites when different metallic parts are in contact.
Used in Corrosion Protection for Metals:
Potassium hydroxyoctaoxodizincatedichromate (1-) is used as a corrosion-inhibiting zinc pigment to protect steel and other metals. The active protection against rust depends on the inhibitor's ability to migrate to the exposed surface once the protective coating has been scratched or damaged. Zinc potassium chromate has a similar solubility range (0.5–1.5 g l-1) to strontium chromate, making it a very effective inhibitor.

Safety Profile

Confirmed carcinogen. Mutation data reported. When heated to decomposition it emits toxic fumes of ZnO and K2O. Used as a corrosion inhibiting pigment and in steel priming. See also CHROMIUM COMPOUNDS and ZINC COMPOUNDS.

Environmental Fate

Chromium (both trivalent and hexavalent) enters the environment from numerous natural and anthropogenic sources. The health hazards of environmental exposure depend on the oxidation state, with Cr(VI) being most toxic. Cr(VI) contamination of groundwater typically occurs from industrial sources such as electroplating or corrosion protection. Contamination of surface water is commonly the result of particulate discharges into the air from manufacturing and cooling towers, with the particulates ultimately settling to either soil or surface waters. For years, Cr(VI) was thought to arise environmentally only as an industrial pollutant but recently unpolluted ground and surface waters have been found to contain Cr(VI) in concentrations that exceed the World Health Organization limit for drinking water (50 mg l-1). Much of the Cr(VI) in the environment is ultimately reduced to the less toxic Cr(III). The reduction may be mediated by various reducing agents such as sulfide compounds, and divalent iron (Fe(II)). In addition, organic matter (e.g., humic acid and fulvic acid) in water or soil may mediate the reduction process. Microbial processes also convert Cr(VI) to Cr(III).

Toxicity evaluation

Chromate is taken up by cells through sulfate channels. Once in the cell it can cause both oxidative and nonoxidative forms of DNA damage. The most dominant form of damage is Cr- DNA adduct formation, a process that occurs in vitro at Cr(VI) concentrations of less than 2 mM. The process involves reduction of Cr(VI) to Cr(III) during the formation of either binary (Cr(III)–DNA) or ternary (ligand–Cr(III)–DNA) adducts. In the ternary adducts, the ligand can be ascorbate (Asc), glutathione (GSH), cysteine, or histidine. In in vitro studies, binary adducts were found to account for 75–95% of the total DNA-bound Cr. Asc, GSH, and cysteine represent the three most important biological reducers of Cr(VI) and are key to formation of the ternary adducts. These ternary adducts are strongly mutagenic. When reducing agents such as Asc are depleted, Cr(VI) reduction leads to the formation of reactive oxygen species which may lead to oxidative damage of DNA. It has also been proposed that depletion of Asc (as via oxidation by Cr(VI)) may impede removal of repressive DNA (methylated cytosine-phosphate-guanine) and histone H3 marks which may modulate gene expression. Chromium(VI) also causes the formation of protein–Cr(III)–DNA cross-links. The formation of these adducts is rare but it has been suggested that they may influence gene specific expression. The damage induced by Cr(VI) leads to dysfunctional DNA replication and transcription, aberrant cell cycle checkpoints, poorly regulated DNA repair mechanisms, inflammatory responses, and the disruption of regulatory genes responsible for the normal balance between cellular survival and death. Disruption of these processes result in neoplastic progression.

InChI:InChI=1/2Cr.K.H2O.8O.2Zn/h;;;1H2;;;;;;;;;;/q;;+1;;;;;;4*-1;2*+2/p-1/r2CrO4.K.H2O.2Zn/c2*2-1(3,4)5;;;;/h;;;1H2;;/q2*-2;+1;;2*+2/p-1