Abstract
Hexamethylenetetramine (HMT) as a vapor phase rust-inhibitor was mixed with various reducing agents and was submitted to accelerated corrosion tests in the presence of various sub-components. The results obtained were as follows: (1) When reducing agents such as cuprous chloride, sodium sulfite, stannous chloride, and sodium nitrite were mixed, the rust-inhibiting effects of these agents were no good except for those of sodium nitrite. (2) A mixture of HMT and sodium nitrite (SN) showed excellent rust-inhibiting effects for iron as a vapor phase rust-inhibitor at the molar ratio of 1:4. (3) The rust-inhibiting effects of HMT-SN system can be explained in terms of the vapor transfer mechanism as follows. Since HMT and SN are hygroscopic, they can reduce corrosion not only by thier removal of moisture, but also by their decomposition due to absorption of moisture. That is, ammonia, one of the decomposition products, neutralizes acidic atmospheres; and formaldehyde and nitrous acid, other decomposition products, give a space effect as reducing agents. In addition, when sodium hydroxide, one of the other decomposition products, directly contacts with iron surfaces, the contact rust-inhibiting effects will be given to iron.
