| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To effectively inhibit the corrosion of a copper-based member in contact with a water system having a low calcium hardness such as an open circulation type cooling water system. <P>SOLUTION: A phosphorus-containing compound, a carboxylic acid group-containing copolymer, an oxidizing substance, and an anticorrosive for an azole-based copper are added to a water system having a calcium hardness of less than 100 mg/L as CaCO<SB POS="POST">3</SB>to thereby inhibit the corrosion of the copper-based member in contact with the water system. The concentration of the oxidizing substance is controlled so that the color development after 10 seconds and 30 seconds from the addition of a reagent by the DPD method corresponds to a free chlorine concentration of 0.5 mg/L or less as Cl<SB POS="POST">2</SB>and 1 mg/L or less as Cl<SB POS="POST">2</SB>, respectively, and the anticorrosive for an azole-based copper is added in an amount corresponding to the required concentration (mg/L) of anticorrosive for azole-based copper calculated by following formula (1) or more, wherein formula (1): the required concentration(mg/L) of anticorrosive for azole-based copper =Px0.2+Sx0.4+Ox10, P: concentration of phosphorus-containing compound (mg/L as PO<SB POS="POST">4</SB><SP POS="POST">3-</SP>), S: concentration of carboxylic acid group-containing copolymer (mg/L as solid content), and O: concentration of oxidizing substance(mg/L as Cl<SB POS="POST">2</SB>) as free chlorine concentration corresponding to the color development after 10 seconds from reagent addition by the DPD method. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
