Influence of the β-phase morphology on the corrosion of the Mg alloy AZ91

This review aims to provide a foundation for the safe and effective use of magnesium (Mg) alloys, including practical guidelines for the service use of Mg alloys in the atmosphere and/or in contact with aqueous solutions. This is to provide support for the rapidly increasing use of Mg in industrial applications, particularly in the automobile industry. These guidelines should be firmly based on a critical analysis of our knowledge of SCC based on (1) service experience, (2) laboratory testing and (3) understanding of the mechanism of SCC, as well as based on an understanding of the Mg corrosion mechanism.

A Critical Review of the Stress Corrosion Cracking (SCC) of Magnesium Alloys

Comparison of ceramic and polymeric membrane permeability and fouling using surface water

The opportunity to give an invited presentation to the Gordon Research Conference - Aqueous Corrosion in 2006 and reflections on the discussion at the conference were used to review our understanding of Mg corrosion mechanism, to generate new insights, to identify gaps in our knowledge and to identify research opportunities.

Recent Insights into the Mechanism of Magnesium Corrosion and Research Suggestions

The approach to maintenance management has changed over the last one hundred years. Over the last few years, the Reliability Engineering and Risk Management Group (RERMG) at the University of Queensland has developed an approach called the strategic maintenance management (SMM) approach. The paper outlines the approach and contrasts it with the current approaches. It then discusses the industry‐university partnership in the implementation of this approach and the current activities at the University of Queensland to assist industry in the implementation of the SMM approach.

Strategic maintenance management

The microstructure of two commercial pipeline steels X52 and X65 was examined to provide a foundation for the understanding of the IGSCC mechanism of pipeline steels Observation of the microstructure was carried out using scanning electron microscopy (SEM) and an analytical electron microscope The microstructure of X52 and X65 pipeline steels shows banding of pearlite rich and ferrite rich areas The ferrite grains were about 10 μm in size with curved grain boundaries There was carbide at the ferrite grain boundaries for X52 steel, and there was circumstantial evidence to suggest carbon segregation at the boundaries The pearlite colonies were consistent with nucleation by a number of different mechanisms

Microstructure of X52 and X65 pipeline steels

Measurement of grain boundary composition for X52 pipeline steel

The purpose of the present investigation was to gain an understanding of the nature of the carbon contamination on the surface of standard steel transmission electron spectroscopy (TEM) specimens, the effect of exposure of a clean specimen to normal laboratory air, and the efficacy of plasma-cleaning treatments. This knowledge is a necessary prerequisite to the development of appropriate specimen preparation and/or specimen cleaning methods. X-ray photoelectron spectroscopy in combination with argon ion beam profiling was used to characterize the specimen surfaces of X65 steel and 316 stainless steel. The only clean carbon-free surface obtained was that during argon etching of the sample in the surface analysis chamber. Any exposure of a previously cleaned sample to laboratory air resulted in a rapid carbon (hydrocarbon) contamination of the sample surface and the development of surface oxidation, Plasma cleaning with subsequent exposure of the specimen to the laboratory air also resulted in a carbon-contaminated surface. This suggests that procedures of preparation of TEM specimens of steels outside an ultrahigh vacuum chamber are unlikely to result in the lowering of contamination rates on specimens to levels where measurements for carbon in the grain boundaries are possible. What is needed is a cleaning system as an integral part of the specimen insertion system into the field-emission scanning transmission electron microscope. This cleaning could be carried out by argon ion etching. Copyright (C) 2000 John Wiley & Sons, Ltd.

Implications of specimen preparation and of surface contamination for the measurement of the grain boundary carbon concentration of steels using x-ray microanalysis in an UHV FESTEM

Grain boundaries of pipeline steel X42 were characterised by electron energy loss spectroscopy (EELS) and with energy dispersive X-ray spectroscopy using a high-resolution analytical electron microscope in order to elucidate its intergranular stress corrosion cracking mechanism. In these experiments, EELS was not a good method contrary to expectation. Carbon contamination on the specimen surface continues to be a issue. Argon plasma cleaning and Precision Ion Polishing System cleaning did not remove the carbon contamination from the sample surface. There were carbide precipitates along ferrite:ferrite grain boundaries, and manganese and carbon were segregated at the ferrite:ferrite grain boundary between the carbides. There was no measurable S and P segregation at the ferrite:ferrite grain boundary. There was no measurable Mn segregation at the ferrite:pearlite grain boundary, which is different to the result for X65 and X52.

J. Q. Wang

Papers

Microstructure of X52 and X65 pipeline steels

Measurement of grain boundary composition for X52 pipeline steel

Implications of specimen preparation and of surface contamination for the measurement of the grain boundary carbon concentration of steels using x-ray microanalysis in an UHV FESTEM

Grain boundary characterization of X42 pipeline steel in relation to IGSCC