Rigorous cleaning techniques

Emersion of an electrode from electrolyte with its double layer intact is now a widely accepted phenomenon and technique. Not only is it a phenomenon which deserves careful consideration and study, but also a process which opens up a new set of experimental methods to the study of the electrochemical double layer. Electrode emersion involves the careful removal of an electrode from electrolyte under potentiostatic control, usually hydrophobically 11-5). When fairly concentrated electrolyte parts ("unzips") from the electrode surface during hydrophobic emersion, the double layer remains essentially intact on the electrode surface and no electrolyte outside the double layer remains. This phenctnenon is not due to the presence of organics or other impurities as seme have suggested. The emersion process works well with rigorously clean electrode surfaces (5). 

Surface analytical techniques such as X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) have allowed a much-improved assessment of the extent of surface contamination (see Volume 1, Chapter 24). The development of more rigorous surface-cleaning regimes has been made possible by an iterative process of employing a given cleaning technique followed by analysis of what has been achieved. 

Hot presses are expensive. 2 Often used without rigorous surface preparation. 3 Plastics and rubber parts not normally cleaned and never with chlorinated solvent. 4 Inexpensive heating techniques available. 5 May need pre-shaping curved surfaces difficult. 

Liquid penetrant inspection. The liquid penetrant NDE method is apphed to detection of faults that have a capillary opening to the test object surface. The nature of this NDE method demands that attention be given to material type, surface condition, and rigor of cleaning. Liquid penetrant inspection can be performed with little capital expenditure, and the materials used are low in cost per use. This technique is applicable to complex shapes and is widely used for general product assurance. 

This technique is easy, completely portable, and highly accurate if performed properly. It detects open-to-the-surface crack indications. Rigorous surface cleaning is required. This technique is applicable only to cleaned surfaces unclean ones will give unsatisfactory results. It is readily used on external and accessible surfaces that have been subjected to minimal corrosion deterioration and can be cleaned. It readily detects any open-to-the-surface cracks, surface defects, and pitting. 

The high reactivity and low concentration of carbanionic active centres makes anionic polymerization very susceptible to inhibition by trace quantities of reactive impurities (e.g. H2O, CO2, O2). Thus all reactants and solvents must be rigorously purified and the reactions must be carried out under inert conditions in scrupulously-clean sealed apparatus. High vacuum techniques are often used for this purpose. 

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