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GERMANY Chemical Reactions of Tin. The behaviour of tin and tin plate under atmospheric conditions, and the problem of corrosion of the exterior of tin cans, are discussed. An interesting detail is the table listing the corrosion, expressed in g./sq.m./day, of milk and some milk products. The tin plate is only 2 micron thick (approximate value). The effects of fruit juices, and of alkaline substances, are described in detail. Corrosion becomes apparent in the form of pitting, hydrogen absorption and change in polarity of the Sn‐Fe system, forming complex salts. Sulphide containing, or forming, substances also act as corrosives and cause discoloration. The constitution and protective effectiveness of lacquers used in the food industry are correlated and discussed.—(K. Heintze and Fr. Braun, Werkstoffe und Korrosion, 1956, 7 (12), 716–723.)

This is the third and last of the series of summaries of papers presented at the Dechema Corrosion Congress held in Frankfurt. Earlier reports of the congress have been given in the January and February issues of CORROSION TECHNOLOGY. This month the summaries are of papers on corrosion prevention methods.

In a number of publications Wirth and Machu have described the measurement of the ion permeability of paint films. In principle, the experimental arrangement used for their first tests consisted of a cell with a weak electrolyte solution containing an iron sheet covered with the paint to be investigated and a sheet of a noble metal ‘silver’ in conductive connection.

Corrosion fatigue observations. Rotating cantilever tests in air and corrosion‐fatigue tests have been made on a high‐purity aluminium‐zinc‐magnesium alloy and on a commercial alloy (D.T.D. 683) in various conditions of heat treatment. The results are compared with special reference to the form of fracture and microstructure. Evolution of gas from active slip zones under corrosion fatigue has been observed. A mechanism for corrosion fatigue in these alloys is discussed.

Although the first part of this article (published in the November issue) is highly relevant to grid corrosion, certain other considerations are also very important, namely, stresses within the grid and grid growth.

The phosphatability of a steel surface and, hence, the corrosion protection achieved is related to the quality of that steel surface. It is the intent of this paper to determine what parameters of the steel surface influence phosphatability. This was done by examining the influence of steel surface roughness and contamination on zinc phosphate coating quality, and by determining the relationship of phosphate coating weight and density to the corrosion resistance of painted steel. A high correlation was found between the amount of corrosion creepback of phosphatized and painted steel substrates and the amount of organic carbon present on the surface of the steel. The carbon, analyzed by Auger Electron Spectroscopy, average approximately 50A in depth and is not removed by phosphate precleaning operations. The carbon inhibits the formation and development of phosphate coatings which are required to provide satisfactory corrosion resistance.

Cathodic corrosion protection. Cathodic corrosion is defined as the corrosion occurring of a metal which, in an electrolytic cell, forms the cathode. This type of corrosion is discussed in detail and a number of valuable data about loss of material due to corrosion, current densities, etc., are given for a variety of conditions.—(W. Thury, Werkstoffe & Korrosion, 1954, 5 (3), 84–87.)

GERMANY Inhibition of hydrogen corrosion of iron by phenyl thiourea. In de‐aerated acid solutions the corrosion of iron is much reduced by very small additions of phenyl thiourea. For a quantitative study of this, stationary current/voltage curves were studied at potentials close to the open‐circuit potential of carbonyl iron in NaClO‐HClO4 solution of pH 2. By control measurements of various kinds it was thus shown that it is possible to obtain the partial current/voltage curves of both iron dissolution and hydrogen deposition with high accuracy. Therefore a quantitative estimation of the anodic and cathodic components of the total inhibition efficiency is possible. With phenyl thiourea it was found that, under the experimental conditions, inhibition was nearly exclusively cathodic up to 10−6 mol/1. inhibitor, with gradually increasing anodic inhibition at higher concentration.—(H. Kaesche, Werks. u. Korr., 1959, 10 (10), 622–624.)

The inhibition of corrosion of B26S aluminium by various colloidal substances in aqueous sodium hydroxide has been studied. The extent of corrosion decreased with increase in the concentration of the inhibition. At an inhibition concentration of 0.5% and above. The efficiency of the colloids in decimolar sodium hydroxide increased in the order: gelatin < dextrin < glue < agar agar < acacia < tragacanth (86%). The efficiency decreased with increase in the concentration of alkali, the P.I. at an inhibitor concentration of 1.5% in 1M sodium hydroxide being, glue (23%), gelatin (39%), dextrin (47%), agar agar (64%), acacia (71%) and tragacanth (86%). The inhibition appears to be due to the absorption of the inhibitor on the aluminium surface. An increase in temperature also decreased the extent of inhibition. The aver‐age energy of activation for corrosion of B26S aluminium in 0.1M sodium hydroxide appeared to be 12.5 KCal, the value in the presence of the inhibitor being somewhat higher.

CORROSION BY OILS Study of the real corrosive power of oils. Known laboratory methods of evaluating the corrosive action of lubricating oils may be divided into two groups: (1) potential action (using e.g. the Pinkevich device and DK‐2, the Underwood apparatus, the YaAZ method, etc.) whereby it is possible to determine not the initial corrosive power of the oil, before the start of test, but that developed during oxidation; and (2) the actual or existing aggressive action. The main distinguishing feature of the second group is that the metal test panel or plate is actually in the oil medium already containing aggressive components, but the test conditions are such (short period) that assume or provide for the practically complete absence of oxidation of the oil during the test itself; so that, in such case, the corrosion is excluded due to formation of oxidation products. The present work includes comparison of corrosive power for different metals, study of effect of acid number of the oil, comparative study of anti‐corrosive effect of various additives for different metals, and concentration curves for these additives. Three references.— (N. M. Grad et al., Zh. prikl. Khim., 1960, 33 (7), 1586–1590.)