11/9/2010
7,828,884
Environmentally pollution-free anti-corrosion pigment composition
Matsuda, Ogawa and Taki of Dai Nippon Toryo, Japan  have developed an environmentally pollution-free, anti-corrosive pigment composition which is free of any heavy metal such as lead and/or chromium, which is free of zinc and/or water-soluble ions and which is excellent in the anti-corrosive effect.  The anti-corrosive pigment composition is based on  condensed calcium phosphate prepared by firing a mixture of calcium and phosphorus compounds with molar ratio (Ca/P=m): 0.50<m<1.00, at a temperature ranging from 180 to 350 C.  The detailed mechanism of the anti-corrosive action of the condensed calcium phosphate as a component of the anti-corrosive pigment composition is not clear, but it appears that the condensed calcium phosphate is slightly dissolved in water under a corrosive atmosphere and it can form metal chelates forming a passive film preventing corrosion.  (RDC 3/15/2011)