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The corrosion behaviour of lead and its alloys in sea‐water is of great commercial interest in view of the considerable use of submerged telecommunications cables and the growing use of lead anodes for cathodic protection of marine structures. This article is concerned with the corrosion of lead in sea‐water and saline solutions and with the anodic behaviour of lead in chloride solutions.

The author first discusses the factors to be considered before deciding on the use of an inhibitor. He then deals in turn with the most important inhibitors, namely sodium chromate, sodium nitrite, sodium benzoate and sodium salts of organic acids, and duplex inhibitors. He concludes with some notes on water treatment and the application of phosphates and silicates. In his first article (August), Dr. Shreir outlined the principles of inhibition.

Tests have been carried out on lead/platinum bielectrodes in sea‐water at 50 A/ft2 for one year to determine the effect of lead alloy compositions on the growth of the lead peroxide. The results indicate that small additions of tellurium or bismuth to a 1 % Ag/Pb alloy are effective in reducing the formation of lead peroxide. Lead/platinum bi‐eleetrodes of suitable lead‐alloy composition, are considered to provide an inexpensive anode material for power‐impressed cathodic protection systems for marine applications.

In the first part of this article, which appeared in March, the theoretical principles of corrosion were applied to practical problems of design, including the choice of the metal of construction and atmospheric corrosion considerations. Now the author describes how design can afford protection against immersed corrosion and corrosion during the finishing process. In his next article, which will be the third in our series, Dr. Shreir will deal with the important subject of cathodic protection and also with underground corrosion in general.

In the first part of his article, which appeared last month, Dr. Shreir discussed underground corrosion and theoretical principles. In this concluding part he describes methods of cathodic protection and then considers the application of the method in chemical and process engineering. Figs. 1 to 6 and references 1 to 16 appeared in the first article.

The application of cathodic protection to buried, submerged or immersed metals has become of increasing importance during the last three decades to civil, structural, mechanical, marine and chemical engineers. Although, at the moment, it has only a limited application for the protection of chemical plant, the method may become more important in this field in the future. The principles of cathodic protection, its applications, advantages and limitations and some of its present uses in protecting chemical plant are considered in the following article.

Last month the author discussed platinum anodes using inert supports such as plastic and ceramic, common metal supports such as copper, and supports with passivating metal such as titanium or platinum. This concluding section discusses applications and operation. It is concluded that only two types of supported platinum electrode can be recommended at present—a platinum‐palladium foil anode with a plastic mount and platinised titanium.

The corrosion of metals can be reduced or prevented by influencing the electrode processes of electrochemical corrosion cells with suitable chemical additions to the corrosive electrolyte. It is the purpose of these articles to consider the mechanism of inhibition, and the applications and limitations of typical inhibitors. This first article is devoted to a consideration of the principles of inhibition in aqueous neutral solutions.

Corrosion studies in the department of metallurgy COURSES in various aspects of metallurgy have been provided by the Sir John Cass College since its foundation as a technical institute in 1902, and in 1928 the Department of Metallurgy commenced systematic courses leading to the B.Sc.(Eng.) degree in metallurgy of the University of London. It is true to say that the syllabus for this degree has largely determined the pattern of metallurgical interests in the department and as little emphasis was placed on corrosion, the subject was naturally neglected.

In the previous article the basic principles of corrosion were considered with particular reference to immersed conditions of attack and it was shown that corrosion resulted from the interaction of the metal and its environment and occurred by a galvanic cell mechanism. It follows, therefore, that anodic attack may be prevented by factors which may be either related to the metal or the environment. It is the purpose of this article to apply the theoretical principles of corrosion to practical problems and to consider in particular how corrosion can frequently be avoided in the earliest stages by attention to design. No particular process will be considered but rather the effect of the metal, method of construction, shape, velocity of flow of the liquid, dissimilar metals in contact, etc., on the possibility of corrosion occurring. Although there are certain basic principles in designing to avoid corrosion, it should be emphasised that this must be followed by pilot‐plant testing, as only in this way can the possibility of corrosion being avoided be confirmed.