孔食が生ずるために, ステンレス鋼のような不働態金属の海水にさらされる構造物への利用や, アルミニウムの飲料水や工業用水に触れる構造物への利用が, 著しく制約を受ける。このような制約を克服する上で, 明確に定義される臨界電位よりも貴な電位においてのみ孔食が発生するという重要な事実が見いだされている。塩化物が存在すれば, 臨界電位は卑な方向に移動する。しかし多くの他の塩類は臨界電位を貴にするので, 臨界電位が腐食電位よりも貴になるまでその塩を加えれば, 塩水中における孔食は有効に防止できる。温度が室温以下になれば, 18-8ステンレス鋼の臨界電位は著しく貴方向に移り, 耐孔食性は向上する。しかしこのことは2.4%Moを含む18-8ステンレス鋼には当てはまらない。アルミニウムの場合の温度の効果は小さい。犠牲陽極を用いるなどカソード分極によって電位を臨界電位以下にすれば, 孔食の発生は有効に防止できる。

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In our previous paper, we suggested that organic corrosion inhibitors could be adsorbed on metal by two ways. One was carried out by electron-donation of the central atom of the adsorbate, and the other by proton-donation. The latter was brought about only when inhibitor molecules had active hydrogens as their constitutional atoms. As the suggestion was derived mainly from weight loss tests conducted in inhibited acid media, more detailed experiments such as from electro-chemical methods were shown in this paper.
As results, dodecylamine which had active hydrogens were more effective than N, N-dimethyldodecylamine which was prepared from dodecylamine by displacing its active hydrogens with methyl radicals. Cetylmercaptan was more effective than methylcetyl sulfide even at room temperature. Generally, S-containing compounds could hardly be adsorbed on metal at room temperature because of their deficient electron donation ability, while cetylmercaptan was more inhibitive than methyl-cetyl sulfide. For this difference, we supposed that mercaptan could be adsorbed on metal by its proton-donating as we could see in hydrogen-bridged compounds.
Dodecylamine and cetylmercaptan could be adsorbed on metal surface both by electron-donation and by proton-donation, but N, N-dimethyldodecylamine and methyl-cetyl sulfide could only by electrondonation. So, the metal surface filmed by N, N-dimethyldodecylamine (or the sulfide) had areas to be adsorbed by dodecylamine (or the mercaptan) by means of their hydrogen-bonding ability, but dodecylamine-filmed surface had no areas to be adsorbed by N, N-dimethyldodecylamine (or the sulfide).

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The effect of magnesium hydroxide water slurry and dolomite powder injection methods for preventing high and low temperature corrosion in heavy oil firing boiler was investigated. The results of the investigation are briefly summarized as follows:
(1) The magnesium hydroxide injection was effective for reduction of low temperature corrosion, and the deposits sticking to boiler surface of high temperature zone turned coarse-grained and brittle.
(2) Decrease of corrosive property of the high temperature zone deposit was also perceived from both change of its chemical composition and rise of its melting point.
(3) Dolomite injection also resulted in reduction of corrosivity of high temperature zone deposit and rise of its melting point.
(4) Calcium oxide in dolomite reacted with sulfur dioxide and sulfur trioxide in combustion. gas on high-temperature zone.
From the above, the additive injection system was confirmed to be a very effective means for various purposes.

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