BASIC ZINC CHROMATE

PRODUCT IDENTIFICATION
CAS NO. 15930-94-6

BASIC ZINC CHROMATE
EINECS NO. 236-878-9
FORMULA CrO4Zn
MOL WT. 181.38

H.S. CODE

  
TOXICITY

 
SYNONYMS  Zinc tetraoxychromate; C.I. 77955; Pigment Yellow 36;
Chromic acid, zinc salt; Chromium zinc oxide; Buttercup Yellow; Chromium zinc hydroxide; Zinc chromate[VI] hydroxide; Zinc chromate oxide, monohydrate; Zinc hydroxychromate; Zinc tetrahydroxychromate; Zinc chrome;
DERIVATION  

CLASSIFICATION

 

PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL STATE yellow powder
MELTING POINT  
BOILING POINT  
SPECIFIC GRAVITY 3.45
SOLUBILITY IN WATER soluble
pH 6 - 8
VAPOR DENSITY  

REFRACTIVE INDEX

 

NFPA RATINGS

  

AUTOIGNITION

  
FLASH POINT  
STABILITY Stable under ordinary conditions.

GENERAL DESCRIPTION  & APPLICATIONS
Chromium (symbol Cr and atomic number 24) occurs in the oxidation states 0, +2, +3, and +6 states. Element (0) and divalent chromium, however, are unstable. Chromium (0) immediately produce a thin oxide layer. Divalent chromium is easily oxidized to the trivalent form in air. The trivalent and hexavalent oxidation states are important in industry, which exit in their divalent anions called chromate and dichromate respectively and an chromic anhydride form called chromium trioxide (CrO3) and chromic oxide (Cr2O3). In industrial, chromium trioxide is called chromic acid. The principal uses of chromium are in the metallurgical processing of ferrochromium and other metallurgical products to impart corrosion resistance, chiefly stainless steel. There are applications in chrome plating, anodizing aluminium, and refractory processing of chrome brick. When combined with oxygen together other metallic elements such as lead and potassium, it forms various inorganic pigments. Chromium is used in chemical processing to produce chromic acid and chromates. Chromates are strong oxidants which will produce many organic and inorganic materials and used in the purification of chemicals. Chromates are used as rust and corrosion inhibitors in diesel engines. Dichromate is converted to chromic sulfate for tanning of leather. The reaction of chromium with collagen raises the hydrothermal stability of the leather and renders it resistant to bacterial attack. The reaction with collagen is useful reaction in screen printing application and in photography as a sensitizer for gelatin coatings. This Chromates and dichromates are used as pigments in paints and in dyeing. Chrome colors include black, red, orange, green, and yellow. Chromate salts contain the chromate ion, CrO4-2, and have an intense yellow color. Dichromate salts contain the dichromate ion, Cr2O7-2, and have an intense orange color. Chromates are used as mordant in dyeing cloth.

Chromic acid ( chromium trioxide, CrO3) is an odorless red deliquescent solid. Chromium trioxide is produced commercially by the reaction of sodium dichromate with concentrated sulfuric acid. It has been used mainly for chromium plating particularly in the production of automobiles and as a colorant in ceramics. Uses in other metal-finishing operations include aluminium anodizing, particularly on military aircraft; chemical conversion coatings, which provide both decoration and corrosion protection; and the production of phosphate films on galvanized iron or steel. It is a powerful oxidant and are utilized by controlled oxidations in organic synthesis. This compound is sensitive to moisture.

Another significant oxygen compound, chromic oxide is prepared by calcining sodium dichromate with boric acid or by reducing sodium dichromate with carbon. Anhydrous chromic oxide is produced commercially from chromic hydroxide, dry ammonium dichromate, or sodium dichromate by heating  with sulfur. Chromic oxide is a dark green, amorphous powder, forming hexagonal crystals on heating that are insoluble in water or acids. Most chromic oxide is used as a pigment. Anhydrous chromic oxide is known as the most stable green pigment used when heat, light and chemical resistance is required for glass, ceramics, and polymers. Its hydrate form is called Guignet's green and used as a green pigment, particularly for automotive finishes.

Chromic compounds are also used in metallurgy in the manufacture of chromium metal and aluminium-chromium master alloys, in refractory brick, and as a chemical intermediate. They have good resistance to alkali and find application as colorant for latex paints. They are used in asphalt roofing and in camouflage paints. They are used as catalyst in the preparation of methanol, butadiene and high-density polyethylene. When used as a mild abrasive for polishing jewellery and fine metal parts, it is known as ¡®green rouge¡¯

Chromic compounds are used extensively as pigments. Chromic acid finds applications in:

  • wood Preservative
  • Metal Plating
  • Magnetic Tape
  • Catalyst
  • Copper stripping
  • Aluminum anodizing
  • Corrosion inhibitor
  • Photography
  • Purifying oil and acetylene
  • Oxidizer in organic synthesis

Basic zinc chromate is the mixtures of various form of zinc chromate including zinc chromate oxides, Zn2(CrO4)O. is prepared from a solution of chromium trioxide or sodium dichromate reacted with zinc oxide. Zinc chromate is used as rust- and corrosion-resistant pigment in paints, varnishes and oil colors. It is used in solvent and vinyl based wash primer wash primers, metal conditioners or in aluminium flake coatings, either alone or in combination with strontium chromate (water based wash primer).

SALES SPECIFICATION

APPEARANCE

Green crystal powder
SPECIFIC GRAVITY

3.45 - 3.50

WATER

1.5% max
TRANSPORTATION
PACKING  
HAZARD CLASS  
UN NO.  
OTHER INFORMATION
CAS RN of Zinc chromates
15930-94-6 (Zinc Chromate Hydroxide)
12206-12-1 (Zinc Chromate Hydroxide)
66516-58-3 (Zinc Chromate Hydroxide)
13530-65-9 (Zinc Chromate)
1308-13-0 (Zinc Chromate)
1328-67-2 (Zinc Chromate)
14675-41-3 (Zinc Chromate)