2687.     PICHLER, H., AND WALENDA, H.  [Formation of Iron Carbonyl in the Action of Carbon Monoxide Upon Steel.]  Brennstoff-Chem., vol. 21, 1940, pp. 133-141; Chem. Abs., vol. 35, 1941, p. 3207.

        Literature is reviewed in work arising from projected use of CO and H₂ with alloy steels at 300° and 1,000 atm.  The heat of formation of liquid Fe(CO)₅ in the equilibrium Fe+5 CO=Fe(CO)₅ was determined as +53.7 kgcal. per mol. at constant volume.  Theoretical and actual temperature-pressure relations were determined by use of filings of 0.15-0.30 mm. low-C steel containing S and P in 48-hr. tests with still and flowing CO, containing 10% N₂, at 100°-250° and 300 atm. starting pressure.  Maximum action in the tests occurred at 270 atm. and 200° in 2 days in still gas.  Equilibrium concentrations of gaseous Fe(CO)₅ decreased sharply from 5% to 0.01% with increasing temperature.  Tests with alloy steels at 200° and 300 atm. showed the 14.2 and 24.4 Cr steels to suffer no weight losses, while a 2.8% Si steel and one containing 1.22% Cb lost 2-3%.  Similar tests at 450 atm. of Cr 14.2 and Ni 0.72% gave no weight loss, but steel containing Cr, 3.18; Mo, 0.64; W, 0.6; and V, 0.12% lost 5-8%.  Large and small steel filings, containing 5.0% Ni, lost 10 and 30%, respectively, the caronyl analysis showing no preferential Ni.  Steel of 2.46% Mn lost over 5%.  Steel of 2.3% V or 1.22 Cb lost 5-8% and one of 5.3 Al lost 1-1.5%.  In tests of nearly 17 days at 6 l. per hr. with rods 40 x 6 mm. diam. in flowing 100% CO at 1,000 atm. and 200°, low-C steel lost 2% in weight.  After heat-treatment its loss was around 7%.  Gray cast iron lost around 75%, retaining its dimensions with a reaction in apparent density from 7.1 to 2.0 and increasing in C from 2.9 to 16% instead of the expected 10-11%.  Metallographic sections showed residual skeletons of phosphide eutectic and ferrite residue.  Two series of tests with rods in 100% CO and CO containing 60% H₂ and 10% N₂ at 1,000 atm. and 200° showed that steel of 3.18% Cr plus small amounts Mo, Si, W, and V lost weight but increased Cr and Si reduced the loss; mixed gas attacked these alloy steels less; steels of 14-28% Cr were unattacked by either gas; steel of Cr 18, Ni 8.9, and Ti 0.53% gained weight; steels of 2.8-4.3% Si were attacked strongly, but 15% Si greatly reduced attack; steels of 5-23% Ni were attacked strongly at the lower Ni; steels of 2.5-13.5% Mn were attacked in les at higher Mn; a 0.4-0.6% Mo steel was attacked strongly by mixed gas; low Cr-Mo-V steels were attacked strongly by both gases as were steels of 2.3% V and 1.22-3.5% Cb.  26 refs.