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 levels (10, 50, 100, 200, and 300 ppm) were used. A copper corrosion rate of up to 1300 mg/m2 d was measured for a period of 21 days using a gravimetric method. The patina layers were characterized using cathodic reduction, X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning 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)2·4H2O]. The latter was formed by both cupric hydroxide and formic acid-cuprous ion complex mechanisms.The authors express their gratitude to the CICYT of Spain for its financial support for project no. QUI97-0666-C02-01. E.C. expresses his gratitude to the Spanish Ministry of Education and Culture for the scholarship granted to him.Peer reviewe