Exfoliation Corrosion of Aluminum Alloys. III. Corrosion Products Converters

The requirements to be met by a converter of the corrosion products (CCPs) of aluminum alloys are formulated, and the technique for expert assessment of its efficiency is developed. Accelerated, field, and strength tests of specimens with the exfoliation corrosion (EC) products incompletely removed were carried out. The effect of both the penetrability of a CCP composition and the surface treatment on the completeness of the EC products transformation and the paint coatings (PCs) adhesion were investigated. The CCP compositions with enhanced physicochemical properties and protective capacity, including those resistant to microbial corrosion, compatible with PCs and exerting no detrimental effect on their adhesion, are revealed.     

Corrosion. A Literature Review

Abstract

Introduction: In contrast to the situation in 1962 and 1963, when, in all, there were seven major international meetings dealing in whole or in part with the subject of corrosion, the year 1964 has seemed to be relatively quiet, at least in so far as interchange of experience and views upon theoretical aspects are concerned. In 1964, there was in fact only one major international meeting—the First European Congress on Marine Corrosion and Fouling, held in Cannes in June.     

Practical Corrosion Problems in Relation to Welded Joints. II. Corrosion Problems in Design

Abstract

This paper deals firstly with the application of protective coatings to welded structures. It then discusses the economic maintenance problems involved, the welding of hollow members, stress corrosion craking and limited life design, and corrosion fatigue. The points made are illustrated by some experimental results.     

Astrakhan–Mangyshlak Water Conduit. The Corrosion State on the Internal Surface and Methods for Its Corrosion Protection. Part I. Corrosion Deposits

The operation conditions of the inner surface of the long-distance Astrakhan–Mangyshlak fresh-water main and the properties of corrosion deposits on it are considered. It is shown that most of the surface operates in a weakly mineralized fresh water with a yearly temperature variation of no more than 14°C and in conditions of almost complete deaeration. The properties and composition of the deposits change along the pipeline symbatically with the water composition.     

Corrosion and Corrosion Inhibition of Reinforcing Steel: II. Embedded In Concrete

Abstract

Reinforcing steel, whether embedded in Portland concrete or Portland cement-blast furnace slag concrete and mixed with distilled or tap water, becomes passivated. On the other hand, when the concrete is mixed with sea water, the steel corrodes severely, and when Helwan mineral water is used for mixing, a borderline condition is obtained. Portland cement-blast furnace slag concrete had poorer corrosion resistance compared with ordinary Portland cement concrete.

Steel passivity is not impaired when Portland cement concrete or Portland cement-blast furnace slag concrete is admixed with up to 8% of sulphates. However, when cement extract is used, the passivity is impaired when as little as 0·2% of sodium sulphate is added.

Additions of some anodic inhibitors such as benzoate, chromate, nitrite, phosphate and stearate to a corrosive concrete medium are efficient in preventing the corrosion of reinforcing steel. The critical concentration for inhibition is higher in the case of Portland cement-blast furnace slag concrete than that of Portland cement concrete. Coating the steel with Portland cement slurry alone or Portland cement slurry containing inhibitors improves the corrosion resistance of steel to some extent but does not inhibit the corrosion in strong attacking media.     

Corrosion in artificial defects. II. Chromate reactions

Artificial defects, in the form of slots, were milled through a chromate-containing protective paint system on AA2024-T3 and exposed to neutral salt spray (NSS). Proton induced X-ray emission (PIXE), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS), electron microprobe analysis (EMPA), and Raman spectroscopy were used to characterise the primer and the alloy surface. Chromate was released by the primer to form a 40 μm depletion zone around the edge of the slot. Within the depletion zone, the chromate was reduced but not completely removed. Chromate was detected in the runoff from the slots and was also found to have reacted with the exposed alloy surface. Chromate was found to react with intermetallic particles, smears formed by the milling process, and pits.     

Corrosion and Corrosion Inhibition of Reinforcing Steel: I. Immersed in Alkaline Solutions

Abstract

The electrochemical behaviour of reinforcing steel in stagnant alkaline solutions, especially calcium hydroxide, has been investigated. It was found that the oxidation processes that take place on steel are determined by the degree of surface oxidation of the sample and by dissolved oxygen, but not by the type of cation present.

In aerated solution, ferrosoferric oxide (Fe₃O₄) is the intermediate oxidation product on the steel surface while ferrous hydroxide is the intermediate product in de-aerated solution.

In pure alkaline solutions, the critical pH above which stable passivity occurs is 11·5. This value increases when the alkaline solution is contaminated with aggressive ions or when reinforcing steel having mill-scale on its surface is used. A linear relationship holds between the pH of the alkaline solution and the highest concentration of sodium chloride that can be tolerated (CC1-): pH = n logCcc^? + K where nand K are constants.

Calcium hydroxide solutions prepared fronl water of different local sources act differently towards steel. Thus, in saturated calcium hydroxide solution prepared from either distilled or tap water, the steel becomes passive. In the corresponding solution in mineral or sea water, the metal corrodes. On the other hand, mineral water becomes inhibitive when the pH is increased to 13. Sea water could not be tolerated by mere increase in pH.     

Corrosion and Protection of Metals: I. The Origin and Rate of Corrosion

Corrosion processes are seen to take place in an energy-dissipating electrochemical cell. The thermodynamics of aqueous corrosion are considered and the importance of both anodic and cathodic processes is highlighted. The rate of a uniform corrosion process is expressed in both S.I. and practical units.