Performance and mechanism of a water stabiliser for low hardness cooling water

Corrosion of carbon steel and copper is a troublesome problem in low hardness cooling water systems. A new kind of water stabiliser containing hydroxy phosphonocarboxylic acid, zinc salts and molybdate has been developed. Its performance has been proved by means of weight loss tests and a static state scale‐inhibiting test method. The mechanism was also studied using polarisation tests, scanning electron microscope examination and XPS analysis. The test results showed that the corrosion rate of carbon steel and copper could be reduced to 0.0136 and 0.0010 mm/a, respectively. A compact film containing P, Mo and Zn was formed on the surface of carbon steel, by means of which the steel was protected.