Copper corrosion mechanism in the presence of formic acid vapor for short exposure times

The rate of copper corrosion originated by the action of formic acid vapors at 100% relative humidity was studied. Five formic vapor concentration lev els (10, 50, 100, 200, and 300 ppm) were used. A copper corrosion rate of u p to 1300 mg/m(2) d was measured for a period of 21 days using a gravimetri c method. The patina layers were characterized using cathodic reduction, X- ray powder diffraction, Fourier transform infrared spectrometry, and scanni ng electron microscopy techniques. Some of the components identified in the corrosion-product layers were cuprite (Cu2O), cupric hydroxide hydrate [Cu (OH)(2). H2O], and copper formate hydrate [Cu(HCOO)(2). 4H(2)O]. The latter was formed by both cupric hydroxide and formic acid-cuprous ion complex me chanisms. (C) 2000 The Electrochemical Society. S0013-4651(99)03-061-X. All rights reserved.