Gregory Cash

The effect of potential scan rate on the parameters used to synthesize anodic polarization curves

Abstract The anodic polarization behaviour of pure iron in near neutral 0.1 M sodium benzoate with and without 0.007 M Cl − at different potential scan rates has been studied. The suitability of a computerized curve matching routine for systems exhibiting the typical active-passive transition and subsequent film breakdown has been demonstrated. The effect of potential scan rate on the input parameters required to generate the anodic polarization curve was established and empirical linear relationships were derived. This leads to the prediction of curves at other scan rates and good matches between the predicted and experimental curves are obtained provided the scan rate is not too far outside the initial range chosen.

Fourier transform infrared spectrometry: a versatile technique for real world samples†

The versatility of FTIR spectrometry was explored by considering a variety of samples drawn from industrial applications, materials science and biomedical research. These samples included polymeric insulators, bauxite ore, clay, human hair and human skin. A range of sampling techniques suitable for these samples is discussed, in particular FTIR microscopy, FTIR emission spectroscopy, attenuated total reflectance and photoacoustic FTIR spectrometry. The power of modern data processing techniques, particularly multivariate analysis, to extract useful information from spectral data is also illustrated.

The corrosion rate of low carbon steel in stationary and stirred sugar juice: A mathematical analysis of polarization curves

Abstract The investigations reported here for the corrosion of low carbon steel in mixed cane sugar juice (i.e. the juice leaving the extraction process) have included a study of the contribution of activation, concentration and resistance polarization to the cathodic reactions. Mathematical methods involving the generation and devolution of polarization curves were used to identify the corrosion reactions. The oxygen reduction reaction appears as the dominant cathodic reaction with both activation and diffusion polarization operative at the corrosion potential. The corrosion rate of the steel can be determined from the anodic polarization curve corrected for surface film resistance.

The corrosion resistance of low carbon steel in flowing sugar juice: The analysis of polarization curves from a laboratory flow system

Abstract A study of the corrosion of mild steel in sugar juice in a laboratory flow rig has shown that oxygen reduction, which is the dominant cathodic reaction and comes under mixed activation and mass transport control, remains the dominant cathodic reaction at flow rates corresponding to normal factory operation and as combined polarization was still observed, the linear polarization resistance method is not applicable. The surface film whose resistance increases with time deposits on the working electrode, leads to a reduction in the corrosion rate and counteracts the increase in corrosion rate expected with an increase in flow rate.

Field Monitoring of the Ageing of Composite High Voltage Insulators

Composite high voltage insulators have been introduced in power networks throughout the world to replace ceramic insulators. Particular advantages include low weight, vandal resistance and lower discharge and electrical interference. The disadvantage, and thus the challenge in management of large populations of composite insulators, is the possible loss of insulation properties on environmental ageing, leading to uncertainty as to the safe useful lifetime of the insulator. One approach which exploits the extensive understanding of the degradation mechanism of elastomers such as EPDM, is to assess the condition of the shed by identifying the oxidation products removed by a non-destructive surface sampling method, including a remote live-line sampling tool. A xylene impregnated swab is used to remove surface material from representative sheds. The swabs are analysed by FT-IR emission spectroscopy (IES) and examination of the carbonyl region of the emission spectrum allows relative amounts of the different oxidation products to be determined. Analysis of a large number of insulators from widely varying environments has shown that there is a variation in the extent of oxidation and product distribution which is consistent with corona discharge, ozone damage and extensive UV exposure. By using cluster analysis on the growing database of insulators which have been sampled, it is possible to determine the predominant mode of degradation in particular geographical locations as well as assessing which commercial insulator showed higher durability in the particular environment. The use of IES has been complemented by diffuse reflectance IR for the analysis of chalking of filler and SEM and XPS analysis on thin slivers of polymer to determine the extent of microcracking, depth of degraded layer and elemental composition. Cluster analysis has also been performed on these data to provide a total picture of the degradation of composite insulators and so guide the procurement, maintenance and replacement strategies of the power distribution authorities.

Localised corrosion of high alloy steels in cane sugar juice

Abstract The corrosion resistance of eight high alloy steels to quiescent and flowing juice in a cane sugar factory has been investigated. All are unlikely to suffer spontaneous pitting corrosion under the conditions that exist in the sugar factory while crushing is in progress. A surface film formed on these alloys which was almost entirely organic in nature. This gave additional resistance to pitting. Provided this film is not disturbed and chloride-free water is used for cleaning, the lower grade alloy steel 3CR12 should be a suitable material for mixed juice lines.