A comparative study on copper corrosion originated by formic and acetic acid vapours

The copper corrosion rate and products originated by the action of formic a nd acetic acid vapours at a 100% relative humidity were studied. Copper spe cimens were exposed to formic and acetic acid vapours for a period of 21 da ys. Five formic and acetic acid vapour concentrations (10, 50, 100, 200 and 300 ppm) were tested. Copper corrosion rates of up to 1300 mg m(-2) d(-1) (mmd) for formic acid and up to 2300 mmd for acetic acid were measured usin g a gravimetric method. The corrosion-product layers were characterised usi ng electrochemical, X-ray powder diffraction and scanning electron microsco py techniques. Some of the compounds identified were: cuprite (Cu2O), for b oth acids; cupric hydroxide monohydrate (Cu(OH)(2) . H2O) and copper format e tetrahydrate (Cu(HCOO)(2) . 4H(2)O), for formic acid; and copper acetate dihydrate (Cu(CH3COO)(2) . 2H(2)O) and copper hydroxide acetate dihydrate ( Cu-4(OH)(CH3COO)(7) . 2H(2)O), for acetic acid. (C) 2001 Kluwer Academic Pu blishers.