Corrosion behaviors of mild steel were investigated by measurement of corrosion loss and stress corrosion cracking tests in methanol and its solutions containing formic acid. In methanol solution containing 0.5 percent formic acid, corrosion rate was maximum at the composition of approximately 98 percent methanol with 2 percent water and was minimum at 85 to 90 percent methanol with 10 to 15 percent of water. General corrosion and pitting corrosion were found in these solutions. Especially at temperatures of 40 to 50 deg C, many pits were observed. In methanol solution containing 0.05 and 0.5 percent formic acid, corrosion loss increased proportionally square root of immersion time. Addition of acid to 85 to 85.5 percent methanol with 14.5 percent water increased corrosion rate in the order of hydrochloric acid, formic acid and acetic acid. Sodium chloride addition to about 85 percent methanol solution containing 0.5 percent formic acid decreased corrosion rate in comparison with non addition. Stress corrosion cracking was not found before 140 hours in U-bend and 3 point bending tests in methanol solution containing formic acid.
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