Kinetics of the Dissolution of Copper in Oxygen-Containing Solutions of Various Chelating Agents

The kinetics of the dissolution of copper in stirred oxygen‐containing solutions of ethylenediamine and several amino acids have been examined and compared with those found earlier for ammonia. In each case, provided that the partial pressure of oxygen exceeds a critical value (below which its transport to the copper surface may be rate limiting), the rate was found to be zero‐order in oxygen and first‐order in the complexing agent. The rate‐determining process is believed to be the chemical attack of the oxygen‐covered copper surface by the complexing agent. At 25°, the rate constants for dissolution by ethylenediamine, glycinate, α‐alaninate, and β‐alaninate were found to be 2.3 × 10 2 , 49, 59, and 11 mg Cu cm −2 hr −1 M −1 . These follow the same order as the stability constants of the corresponding cupric complexes. In each system there is also another reaction path, independent of the first, which involves the protonated species, i.e., the ethylenediaminium ion and the neutral amino acids. The corresponding rate constants are 5.1 × 10 2 , 31, 36, and 3.5 mg Cu cm −2 hr −1 M −1 .