Patent ID: 8163105
Filing Date: 2012-04-24
Classification: C23C,C23F

Abstract:
1. A corrosion inhibition method for a surface of an iron-based metallic member of a water system, comprising: adding at least one anticorrosive to the water system, said at least one anticorrosive being selected from a group consisting of pyrophosphoric acids and pyrophosphates, wherein said at least one anticorrosive is added such that a total phosphate concentration of the water system is in a range of from 20 mg to 70 mg-PO forming a first protective film of iron pyrophosphate by adjusting an initial pH at a start of an initial protective film formation process to be 5 or more and less than 7 and eluting iron ions from the iron-based metallic member, terminating the formation of the first protective film by increasing the pH to 7 or more, and forming a second film containing phosphate and calcium on the surface of the first protective film by maintaining the pH of 7 or more.