1281.    GUILLEMIN, A.  [Corrosion of Metals by Methanol.]  Ann. Chim. vol. 19, 1944, pp. 145-201; Chem. Abs., vol. 40, 1946, p. 1437-1438.

       Corrosion of metals by MeOH was studied at room temperature.   Al, Cu, Sn, Pb, Zn, Cd, Sb, Bi, Cr, Fe, Ni, Co were subjected during 4 months to anhydrous MeOH, MeOH containing 20% H₂O, MeOH containing 2% CH₂O, MeOH containing 1% HCOOH, and 1% aqueous HCOOH.  Most of the metals were of 99.9+% purity, Ni 99.8%, Cd 99.5+%, Bi 99-100%, Co 98-99%.  Pure MeOH attacked only Pb, Sb, Al, and Su.  In the presence of 20% water Al and Su are protected by an oxide layer and are not attacked; the corrosion of Pb is reduced; Zn, Cd, Fe, and Co are attacked.  Only Pb and Sb are attacked by MeOH containing 2% CH₂O·MeOH containing 1% HCOOH corrodes most metals, particularly Pb, Zn, Cd, Fe, Ni, Co, Cu, and Sb.  Al is barely attacked, and Cr, Sn, Bi are not attacked.  In 1% aqueous HCOOH solution Cu is not attacked; Pb is attacked much less than in MeOH solution; the corrosion of Al is much stronger; and Sn and Bi are slightly attacked.  The results are tabulated and expressed in weight loss per 100 gm., and weight loss per 100 cm.²  The experiments were carried out in the dark.  The apparent importance of the presence of HCOOH led to the study of the mechanism of the corrosion of Fe, Zn, and Cu by MeOH containing traces of that acid.  In the presence of air MeOH containing HCOOH reacts with Fe with formation of dimethyoxyferric formate.  HCOOFe(OMe)₂ (I).  In an anhydrous solution Zn forms a basic formate, 4 (HCOOZnOH)·-ZnO, and in the presence of water a neutral hydrate, (HCOO)₂Zn·2H₂O.  Cu forms a mixture of basic formates.  In the absence of air Fe dissolves with formation of neutral ferrous formate; Zn is not attacked; Cu is protected by the formation of an insoluble cuprous formate.  Zn and Cu undergo surface oxidation.  The formation of Pb(OMe)₂ is attributed to an initial surface oxidation; in the absence of air Pb is not attacked by MeOH.  (I) was successively hydrolyzed to ferric dihydroxyformate, HCOOFe(OH)₂, and to the neutral formate and Fe(OH)₃.  Calcination at 250° of (I) gave pure, pyrophoric Fe.  The complete hydrolysis of the basic Zn formate gave neutral Zn formate and Zn(OH)₂.  In the presence of sunlight or ultraviolet radiation, Fe is attacked by pure MeOH with formation of (I); this proves that MeOH is partly oxidized to HCOOH.  In MeOH containing HCOOH bronzes and Al bronzes were etched (this can serve for micrographic studies); steel containing 13% Cr was not attacked; steel containing 12% Ni was attacked less than steels containing 2%, 3%, 5% Ni; the latter were attacked as rapidly as pure Fe.

       GUIOT-GUILLAN, G.  See abs. 1055.