アルミニウムに対するヘキサメチレンテトラミン複合防錆剤の効果

気相防錆剤に関する研究 (第5報)

抄録

Vapor phase rust-inhibiting papers, powders and tablets for aluminum were prepared of the composite rust-inhibitors that were mixtures of hexamethylenetetramine (HMT) and sodium nitrite. The optimum composition for the rust-inhibiting effect was elucidated and the rust-inhibiting mechanism was investigated. The results are summarized as follows: 1) The rust-inhibiting papers and tablets showed a good rust-inhibiting effect when the molar ratio of HMT to sodium nitrite was 1:4. 2) For the vapor phase rust-inhibiting papers, the binders such as milk casein and gum arabic showed excelllent effects, when the contents were 6 and 7% respectively. 3) The composite rust-inhibiting powders gave an adverse effect, because the extenders contacted directly with a surface of aluminum. 4) In the case of vapor phase rust-inhibiting tablets, the addition higher than 25% of the composite rust-inhibitor showed an excellent rust-inhibiting effect. 5) The rust-inhibiting mechanism was explained from the following presumption. Since HMT and sodium nitrite are hygroscopic, they reduce moisture which induces corrosion. Moreover, they decompose on absorption of water and, of the decomposition products, formaldehyde and nitrous acid prevent surface corrosion of aluminum by the reducing action and ammonia neutralizes acidic substances in the sealed atmosphere.