THE CHEMICAL CORROSION RESISTANCE OF COMMERCIALLY PURE TITANIUM AND THE INFLUENCE OF ITS CARBON CONTENT ON THE PROPERTY

Abstract

The influences of carbon content on the various properties of commercial pure titanium have been studied in our laboratory, and the report on the effects of carbon on the mechanical properties, fabricating properties and heat treatment properties was already published in the "Light Metals", No. 12 (Aug., 1954 issue).This paper reports on the influence of carbon on the chemical coroosion resistance on the commercially pure titanium.Titanium, which has excellent chemical corrosion resistance, is being utilized as a construction material in the field of chemical, petroleum and synthetic fibre industries in the place of the conventional corrosion resistant metals such as stainless steel, stellite and hastelloy. And reflecting the situation, various reports on the chemical corrosion properties of titanium have already appeared in domestic and foreign literatures.We, also, conducted experiments on the property using the commercially pure titanium which was produced in our plant. Compared with previous papers on corrosion properties, our report is characterized in the following points:(1) The influence of carbon on the corrosion properties was studied.(2) The standard single electrode potential of titanium and other metal was calculated, and the corrosion resistance of titanium was examined from that view point.(3) The hydrogen and oxygen contents in specimens were analysed by the N. R. C. vacuum fusion gas analysis apparatus before and after dipping test.As the result we obtained the following conclusion:(1) Kobe Steel Work's titanium has excellent corrosion resistance against almost all chemical reagents except the following cases: a. HCl 20°C, >90%; boil, >1% e. AlCl3 boil, >25% b. HF f. Oxalic acid boil, >0.5% c. H2SO4 20°C, >70%; boil; >1% g. Formic acid boil, >25% d. H3PO4 boil, >10% h. Trichlor acetic acid 100°C 100%(2) Carbon content in the specimens has no influence on the corrosion propreties when in the range of 0.05-0.12%.(3) As the result of theoretical calculation of the standard single electrode potential, it was clarified that the position of titanium in the ionization series was between aluminium and zinc.(4) By means of gas analysis by the N. R. C. vacuum fusion gas analysis apparatus it was confirmed that-a. When titanium was dipped in the nonoxidizing acid such as HCl or H2SO4, the hydrogen content in the specimens increased remarkably, while oxygen content after dipping was nearly equal as before dipping.b. When titanium was dipped in the oxidizing acid such as HNO3, both hydrogen and oxygen contents did not increase and kept the original value.