Weight loss and potentiostatic techniques Were Used at 25, 35 and 45 degrees C to investigate the corrosion behaviour of mild steel in aqueous solution of formic acid containing different amounts of acetic acid, maintaining the total concentration of the acids at 20%. It was found that the corrosion rate of mild steel ill the mixture Of the two acids is a function of acid composition and temperature. The maximum corrosion rate was observed in 20:0% (formic: acetic) acid solutions by both techniques. The corrosion rate of mild steel in the aqueous mixture of formic and acetic acid having different compositions (%) followed the order 20:0> 19: 1 > 1 8:2> 15:5> 10: 10. Active corrosion behaviour of mild steel was observed over the whole range of potentials at each composition and temperature. The cathodic polarisation curves were almost identical irrespective of the composition of the two acids in the mixture.