Corrosion rates of mild steel in 5-10% hydrochloric, phosphoric or sulfuric acid at several temperature below boiling point were investigated by adding sulphur or nitrogen containing organic inhibitors at the range of 0.05-0.5% concentration. The results indicate that there exists the minimum corrosion rate with the addition of optimum quantities of inhibitors. This may be explained by the fact that in the presence of optimum quantity of inhibitor there exists minimum corrosion rate due to the degree of compactness of adsorption films and that the degree of compactness depends upon the current intensity of inhibitor molecules according to the electric theory i=ρv.

View full abstract

Corrosion rate of mild steel in phosphoric acid or sulfuric acid were studied using one kind or a mixture of 2 or 3 kinds of nitrogen or sulphur containing organic inhibitors.
The results indicate as follows:
(1) Inhibiting efficiency of the mixture is excellent compared with the case in which one kind of inhibitor is used.
(2) Some inhibitors react as corrosion stimulator when singly used in different kinds of acid, but when they are mixed with one or two other inhibitors they behave as excellent inhibitors.
The cause of these phenomena is considered as the formation of compact films of inhibitor molecules, which are polarized by the effect of electric field and great dielectric constant in solution. Such adsorption film becomes compact, when 2 or 3 kinds of inhibitor molecules are adsorbed.

View full abstract

To confirm the idea described in previous reports, some experiments have been carried on as follows.
(1) Corrosion rate of mild steel in hydrochroric, phosphoric, or sulfuric acid was measured, either with the addition of alcoholic compound singly, or with the addition of alcoholic compound in combination with sulfur or nitrogen containing inhibitors, or with the addition of alcoholic compound with chromate for the purpose of preventing pitting corrosion.
(2) In the case of phosphate film on mild steel, the character of film and the speed of film formation were measured with the addition of nitrate to the solution.
(3) Corrosion rate of mild steel dipped in industrial water or sea water with the addition of ordinary inhibitors was measured.
It became clear that the idea expressed in previous reports is applicable to wide range by this experiments. And a new idea about pitting corrosion is inferred as follows: -
Probably a kind of electric condenser is constructed due to adsorptive films, and energies to be accumulated in the condenser will be transported to iron surface through the small holes in the films.
Pitting corrosion occures at the bottom surface of these small holes.

View full abstract

This is a report of a procedure adopted in designing the drainage system and other corrosion control provisions for a pipe line. The steps taken were as follows: (1) pipeline route was determined; (2) ground potentials along the route with reference to a fixed sufficiently remote ground potential were measured with recording instruments, and ground potential distribution profile of the route was obtained; (3) pipe-to-ground potential distribution along the route was anticipated according to the above cited ground potential distribution profile; (4) specifications for the pipe protective coating and covering, locations of drainage equipments and their current ratings were determined; (5) pipes and other necessary materials were prepared and installed; (6) after the pipe line construction work was completed the pipe-to-ground potential distribution profile was obtained to check the adequacy of the design. Thus the adequacy of the design was confirmed.

View full abstract