抄録
Corrosion behaviours of mild steel were investigated by measurement of corrosion loss and stress corrosion cracking tests in methanol and its solutons containing formic acid. In methanol solution containing 0.5% formic acid, corrosion rate was maximum at the composition of approximately 98% methanol with 2% water and was minimum at 85 to 90% methanol with 10 to 15% of water. General corrosion and pitting corrosion were found in these solutions. Especially at temperatures of 40 to 50°C, many pits were observed. In methanol solution containing 0.05 and 0.5% formic acid, corrosion loss increased proportionally square root of immersion time. Addition of acid to 85 to 85.5% methanol with 14.5% water increased corrosion rate in the order of hydrochloric acid, formic acid and acetic acid. Sodium chloride addition to about 85% methanol solution containing 0.5% 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.
