The thermogalvanic corrosion of mild steel in alkaline solution—I. Actively dissolving electrodes

Using a simple model it has been shown that both thermodynamic and kinetic factors contribute to the temperature coefficient of the corrosion potential of a freely corroding electrode when the local action processes are under activation control. In the particular case of a 0·21%C steel immersed in deaerated Na₂B₄O₇/HCl buffer solution (pH 7·6) the kinetic factors predominate resulting in a negative coefficient. A thermogalvanic cell with a hot anode is therefore formed when when two such electrodes, maintained at different temperatures, are connected. In the absence of a significant cell internal resistance, a current will flow which reflects a stimulation of corrosion at the anode and a corresponding protection of the cathode, both attributable to thermogalvanic action. When the thermal e.m.f. is small the cell current overestimates the increased corrosion damage; since the individual electrodes are barely polarized it follows that the kinetics of the local action cathodic process at the anode cannot be ignored.     

The thermogalvanic corrosion of mild steel in alkaline solution—III. The factors controlling etching,passivation and pitting

The thermogalvanic behaviour of mild steel in an environment where active dissolution, passivation and breakdown are all possible has been investigated. The polarity of the electrodes and the magnitude of the cell currents vary with time as these processes occur successively but at different rates at each electrode. In the presence of an aggressive ion the onset of passivity is often undesirable since localized breakdown may ensue, any subsequent thermogalvanic corrosion being predominantly located at the pit sites giving rise to a disproportionate increase in metal penetration relative to the recorded current. Since maximum cell currents of approaching 5 A/m² are possible in these systems, the cells are usually under resistance control; any circumstance which leads to a lowering of this resistance will therefore increase the metal loss. However, thermogalvanic action does not always stimulate the overall corrosion rate of the anode but may, by polarization of this electrode, induce passivity and breakdown at a metal surface which would not undergo these changes spontaneously. Although the metal loss is often lowered, the penetration commonly increases since the corrosion damage which was previously uniform becomes highly localized.     

The organic content of international reference samples of asbestos

Union International Contre le Cancer (U.I.C.C.) reference standard asbestos samples have been extracted with pentane and the organic material in the extract has been examined by gas chromatography. Mass spectrometry was used to provide supporting evidence of the presence of some components identified in the chromatograms.Ultraviolet and fluorescence spectra of the extracted oils indicated that polycyclic aromatic hydrocarbons were a minor constituent of the organic extract.More than sixty components were observed in each of the five pentane extracts. By far the greatest proportion of the extracted material was comprised of a homologous series of n-alkanes.