Pitting Corrosion of Copper in Aqueous Solutions Containing Phosphonic Acid as an Inhibitor
Yutaka Yamada, Osami Seri, Kosuke Tagashira, Koji Nagata
pp. 558-563
抄録
The pitting corrosion of copper in cold water containing inhibitors composed of amino trimethylene phosphonic acid (ATMP), benzotriazole (BTA) and zinc sulfate (ZnSO4) has been studied by the immersion test and electrochemical measurements. The results obtained are summarized as follows: 1) the pitting corrosion of copper did not occur in cold water containing ATMP, ATMP+BTA and ATMP+ZnSO4, respectively. Pitting occurred in cold water containing both ATMP+BTA+ZnSO4 and ATMP+BTA+Na2SO4. The pH value of water lowered to 3. The presence of SO42- in ATMP+BTA solution is essential for the occurrence of pitting corrosion in copper. 2) In the immersion test, pitting corrosion of copper occurred under the presence of SO42- more than 0.6ppm in ATMP+BTA solution. 3) The pitting corrosion easily occurred and the number of pits increased, corrosion potential and breakdown potential became less noble with increase in SO42- concentration from 0 to 180ppm.