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This investigation aims to find the degree of passivation required to completely inhibit the stress corrosion cracking of carbon steel exposed to CO-CO₂-H₂O environments.

A516 pressure vessel steel was exposed to distilled water with 25 per cent CO and 75 per cent CO₂ at an overall pressure of 800 kPa with the introduction of potassium bichromate as an additional inhibitor. Slow strain-rate tests were performed to evaluate the steel for sensitivity to cracking. Electrochemical characteristics were investigated in parallel in order to determine the extent of passivation required with the addition of the inhibitor.

Slow strain-rate tests showed that between 100 and 1,000 ppm potassium bichromate was required to completely mitigate cracking with a significant reduction in passivation current densities.

The chosen inhibitor is not ideal for practical applications as an inhibitor, but gave an indication of the passivation required.

The results showed that the added inhibitor might even cause increased sensitivity to cracking in this environment, with significant passivation required for resistance to cracking.

The degree of passivation required for complete resistance of carbon steel in 25 per cent CO-75 per cent CO₂-H₂O.

The purpose of this paper is to study the effect of heat treatment (HT) applied to an API X60 steel in corrosion resistance and stress corrosion cracking (SCC) susceptibility through slow strain rate tests (SSRT) in NS4 solution and congenital water (CW) to assess external and internal SCC, respectively.

API X60 steel was heat treated at a temperature of 1,200°C for 30 min followed by water quenching. Specimens from this steel were machined according to NACE TM 198. SSRT were performed in a constant extension rate tests (CERT) machine at room temperature at a strain rate of 1 × 10^–6 s^–1. For this purpose, a glass cell was used. Corrosion behavior was evaluated through polarization curves (PCs).

The SCC index obtained from SSRT indicates that the steel heat treated could be susceptible to SCC in CW and NS4 solution; the mechanism of SCC was hydrogen embrittlement. Thus, CW may promote the SCC phenomenon in pipelines. HT improves the steel corrosion resistance. Higher corrosion rate (CR) was observed when the steel is exposed to CW. The corrosion process in X60 steel shows that the oxidation reaction in the anodic branch corresponds to an activation process, and the cathode branches reveal a diffusion process.

The purpose of the heat treatment applied to X60 steel was to generate a microstructure of acicular ferrite to improve the corrosion resistance and SCC behavior.

The purpose of this work was to study the cracking susceptibility of a 7017 aluminium alloy, after anodising under various conditions.

Slow strain tests in dry air, laboratory air and sodium chloride solution were employed. Anodic oxide films were produced with various applied current densities and thicknesses, in horizontal or vertical orientation of the coatings, at the free corrosion potential and also at various anodic or cathodic potentials. For the interpretation of the results, a metallographic study of the specimens before and after straining to failure was carried out using a scanning electron microscope.

The behaviour of anodic coatings was found to depend very much on the anodising conditions. The coatings reduced the ductility of the alloy in dry air but can actually increase the ductility in laboratory air and in 3.5 per cent sodium chloride solution. In most cases, the ductility of coated specimens was greater in 3.5 per cent NaCl solution than in dry air, possibly due to crack blunting by the aggressive environment. Anodic coatings moved the free corrosion potential of the alloy in the noble direction and both the anodised and the bare alloy generally suffered a reduction in ductility at potentials anodic or cathodic to the free corrosion potential, the fall being more rapid for the anodised alloy.

The mechanism causing the increased ductility of coated specimens in 3.5 per cent NaCl solution than in dry air remains yet to be confirmed.

The selection of suitable anodic coatings for the protection of aluminium alloys against stress corrosion cracking depends on the anodising conditions.

The paper provides information regarding the influence of anodising conditions on the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.

This paper aims to determine the effect of water on the SCC of low carbon steel in ethanol in the absence of supporting salts.

Slow strain rate test was done to determine SCC susceptibility. Fractured samples were examined using optical microscopy and scanning electron microscopy.

While the results demonstrated that water alone had no effect on the SCC susceptibility of low carbon steel in ethanol, 2.5 volume per cent moisture gave indications of cracking tendencies.

With South Africa and the world over turning to bioethanol and ethanol blended fuels as a means of reducing its carbon foot print, there are concerns over the corrosive nature of ethanol on common engineering metals like low carbon steels.