Electrode enamel

In enamelled tanks with protection electrodes of low current output, fittings [e.g., heating surfaces (cathodic components)] must be electrically isolated from the tank and the ground. Figure 20-2 shows such a bushing. Smaller cathodic components which take up only negligible protection current (e.g., temperature probes) do not need to be insulated. 

Often it is necessary in designing a cathodic-protection system to know the conductivity of a protective coating (e.g. bitumen enamel) on a structure. This measurement is usually carried out by finding the resistance between an electrode of known area placed in contact with the coating and the structure itself. The electrode placed on the structure can be either of thin metal foil or, preferably, of material such as flannel soaked in weak acidic solution. The resistance between the pad and the metal is measured by means of either a resistivity meter, as previously described, or a battery with a voltmeter and an ammeter or microammeter. Generally speaking, in field work where such measurements have to be made, a resistivity meter is preferable. 

Typical pilot process conditions are Reactor 4001 steel enamel tank. Electrolyzer -10 bipolar electrodes with a surface of 0.9 m2/300 A. A suspension of 1 kmol MnS04 H20 in 535 kg H2S04 [55-60%] at 85 °C is circulated from the tank to the electrolyzer. 

The major use of coal tar pitch is as the binder for aluminum smelting electrodes. Pitch is also used in roofing, surface coatings, and for pitch coke production. Pipe-coating enamels made from pitch are used to protect buried oil, gas, and water pipes from corrosion (IARC 1985). 

The discovery of the element hafnium provides a further example of a missed opportunity to turn scientific achievement into practical application. Hafnium was discovered at Niels Bohr s institute in Copenhagen in 1923 and quickly turned out to be fairly abundant and of potential industrial interest. However, no Danish chemical company seems to have taken an interest in the discovery. The two discoverers, Hevesy and Dirk Coster, sold the patent rights to the Philips firm in the Netherlands. Philips at once took out several patents on the use of hafnium compounds and developed methods for applying the metal in electrodes, filaments and fireproof enamels. ... 

In cathodic delamination, the delamination rate of an organic coating under a cathodic potential depends upon the applied potential, electrolyte solution, and metal substrate (22,25). Cathodic delamination tests were conducted for all three commercial paints. As an example, Figure 5 shows the cathodic delamination plots of control alkyd enamel and water-reducible ISPC coated on bare CRS coupons. Curves Sa and 5b represent delamination area for the control alkyd enamel and the water-reducible ISPC formulation, respectively curves 5c and 5d are the respective plots of delamination current for the two formulations. The delamination test was conducted in a 3% NaCI solution the alkyd coated CRS coupon served as a cathode and was polarized at -I.IV versus a saturated calomel electrode. A significantly slower delamination rate was obtained for the ISPC formula (curve 5b) as compared to the control alkyd enamel (curve 5a). At 44 hours of delamination time, the entire painted area of the working electrode (almost 20 cm x 20 cm) for the control alkyd paint had been delaminated, whereas the delamination area of the water-reducible ISPC was only as little as 1 cm indicating a remarkable coating adhesion improvement for the alkyd ISPC painted on bare CRS coupon. 

Microtool electrodes with different disk heights at the front end can be fabricated by controlling the length of insulation applied at the front end of the microrod. Enamel was used for insulation, and it was first applied on a glass plate as a uniform layer. Then the front end of the microtool was dipped in it immediately. The insulation was dried in air for a few minutes, and the insulation length was measured. 

Uses Pigment for paper, textile printing, water paints, shoe creams, ceramics (electro-ceramics, welding electrodes, glass, glazes, vitreous enamels)... 

The use of ion-selective electrodes in dental and mineralised tissue studies is quite extensive [162,190,192,197,288—360] and particular attention has been devoted to fluoride in saliva and enamel. 

The fluoride electrode has dramatically extended in vivo and in vitro studies on the relation between fluoride in tooth enamel and the incidence of dental caries and the incorporation of fluoride from ingested and topical fluorides. 

The well-known fluoride gradient decreases very sharply with depth from the enamel tooth surface towards the amelo-dentinal junction [318,350,251]. Minor variations in the thickness of outermost enamel layers can profoundly affect analysis unless proper care is exercised to avoid extraneous contamination. Biopsy techniques are thus difficult since sampling alters teeth surfaces and two identical surface areas do not exist [318]. Abrasion with silicon carbide-glycerol slurries for less than 1 min has proved quite satisfactory for this purpose. Samples of about 40 /ig, and equivalent to about 0.3 jum enamel, are either collected in plastic [351] or rubber cups [318], dissolved in 0.5 M perchloric acid and analysed directly with the fluoride electrode. Most teeth except those posteriorly located can be analysed by the abrasion technique. 

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