Pitting corrosion of low alloy steels in simulated low pressure steam turbine environments

This study has examined the pitting tendency of A-470, GFA and S231 turbine rotor disc low alloy steels (LAS) under conditions representative of a contaminated turbine environment. Corrosion potential-time curves and potentiodynamic polarization methods have been used to determine pitting characteristics whilst surface analysis techniques were used to characterize the nature of the passive films formed and the corrosion products in the pits and the surrounding areas. The study demonstrated the suitability of a computerized curve matching routine (SYMADEC) for SYnthesizing, MAtching and DEConvolution of polarization curves typical of those observed for metals exhibiting active-passive behaviour and subsequent film breakdown. Pure iron in nitrogen purged 0.1 M sodium benzoate was chosen as a model system. Potentiodynamic scan rate affects the shape of anodic curves and the influence of this variable on the input parameters required to synthesize an anodic polarization curve was established. Empirical linear relationships were derived over the scan rate selected and this lead to the prediction of curves at other scan rates which were good matches with the experimental curves provided the scan rate was not too far outside the original range chosen. SYMADEC was used to analyze the experimental polarization curves for A-470 steel in a simulated turbine environment. A solution containing 2 ppm NaCl, 2 ppm Na2S04 , 2 ppm NaOH and 5 ppm Si02 was employed as a background electrolyte. The effect of the dissolved oxygen (D02) level on the input parameters used to synthesize curves to match experimental ones obtained in different D02 media was established. Comparison with the same input parameters required to match curves obtained at different potential scan rates showed a similar trend indicating that a comparable polarizing effect can be achieved by increasing the D02 level of the electrolyte

Interfacial ageing of high temperature carbon/bismaleimide composites

Ageing studies were performed on a carbon fibre-bismaleimide (CBR320/328) system developed by the CSIRO in Australia, with a fibre volume fraction of 55%. This material has a glass transition temperature of 302°C and the effect of ageing at 204 and 250

Interfacial ageing of high temperature carbon/bismaleimide composites

Ageing studies were performed on a carbon fibre–bismaleimide (CBR320/328) system developed by the CSIRO in Australia, with a fibre volume fraction of 55%. This material has a glass transition temperature of 302 °C and the effect of ageing at 204 and 250 °C on the interfacial region was studied. A variety of test techniques were employed to characterise interfacial property changes (mode I delamination, SEM, Raman); chemical changes due to ageing (Raman, FTIR); changes in glass transition temperature (DMTA) and weight loss. The results showed that both interfacial and resin degradation mechanisms differed between the two temperatures. It can, therefore, be concluded that accelerated ageing is not applicable to this system

The truth is in there: Analysis of grave relics to help solve a mystery linked to the loss of the HMAS Sydney II

In February 1942, three months after the HMAS Sydney II sank off the coast of Western Australia, taking with it all 645 crew members, the unidentified body of a man washed ashore in a Carley float on Christmas Island. The body was buried and two eyewitness accounts of the situation recorded. A 2006 recovery mission to find the grave site and give the unknown sailor a proper burial was successful. Relics found in the original grave included four somewhat degraded and corroded press-studs–the only remaining components of the sailor’s clothing. These relics were accessioned into the Australian War Memorial’s collection. Analysis of some of the press-studs was conducted in an attempt to help determine who this sailor may have been, or whether he was likely to have been from the HMAS Sydney II. Elemental and molecular analyses using a range of instrumental techniques including X-ray fluorescence (XRF), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray tomography, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) have been conducted in conjunction with the Australian Federal Police and Australian National University. Strong evidence for an inscription on one of the press-studs and a blue colourant from fragments of fabric preserved within the press-studs have been revealed.</p