Patent ID: 6461449
Filing Date: 2002-10-08
Classification: C23C

Abstract:
A liquid composition of matter suitable for forming a chromium containing conversion coating on a metal surface when contacted therewith, said composition having both of the following properties (A) and (B):(A) the composition comprises water and the following components: (A.1) dissolved ions and/or molecules that contain hexavalent chromium atoms; (A.2) dissolved trivalent chromium cations; (A.3) dissolved nitrate ions; (A.4) dissolved cations of one or more metals selected from the group consisting of Ni, Co, Zn and Al; and (A.5) dissolved phosphate ions; and (B) in the liquid treatment composition: (B.1) a molar ratio of dissolved trivalent chromium ions to hexavalent chromium atoms is in a range from 0.11:1.0 to 1.0:1.0; (B.2) a molar ratio of nitrate ions to a sum of hexavalent chromium atoms and trivalent chromium cations is in a range from 2.1:1.0 to 5.5.:1.0; (B.3) a molar ratio of the total of dissolved metal cations selected from the group consisting of Ni, Co, Zn and At to nitrate ions is in a range from 0.05:1.0 to 1.0:1.0; (B.4) a molar ratio of dissolved phosphate ions to a sum of hexavalent chromium atoms and trivalent chromium cations is not more than 0.3:1.