Area effect

Area effects in galvanic corrosion are very important. An unfavorable area ratio is a large cathode and a small anode. Corrosion of the anode may be 100 to 1,000 times greater than if the two areas were the same. This is the reason why stainless steels are susceptible to rapid pitting in some environments. Steel rivets in a copper plate will corrode much more severely than a steel plate with copper rivets. 

Coat both materials or the noble material. Do not coat just the active material (see Area effects above). Coatings should be maintained, especially the one covering the active member of the couple. Use of cathodic protection systems in association with coatings is often recommended. 

Surface area effects in mass transfer or heterogeneous reactions... 

Noble metals should be specified for major structural units or components, particularly if the design requires that these are smaller than adjoining units. There is an unfavorable area effect of small anode and large cathode. Corrosion of a relatively small anodic area can be 100-1000 times more severe than the corrosion of bimetallic components, which have the same area submerged in a conductive medium. Hence, less noble (anodic) components should be made larger or thicker to allow for corrosion. In addition, provision should be made for easy replacement of the less noble components. 

Identify possible emission sources, occupational areas, effects of environmental parameters, needs for enclosure and ventilation equipment. 

A beam from an actual sample will require a more elaborate slit S3rstem for collimation if the sample is broad. The Soller slit (Figure 4-7), a stack of thin parallel plates, is such a system. The reasoning that supports this construction is as follows. Were the sample a point or a line source, a slit between sample and crystal or a slit between crystal and detector would be enough for satisfactory collimation. With a two-dimensional sample, both slits would be needed to get this done. But this arrangement is wasteful of emitted intensity because the detector sees the sample as a line source. To use all the sample area effectively, a system of parallel slits is needed. To eliminate the divergent rays in such a system, the slits must be extended in the direction of the beam, and this leads to the parallel-plate construction in the Seller slit system. 

SURFACE AREA EFFECTS IN MASS TRANSFER OR HETEROGENEOUS REACTIONS 51... 

Substances Hazardous to Health, See also Toxic chemicals, 19, 138, 140 Substitution, 133 Sulphur, 30 Sulphur dioxide first aid, 280, 306 physical properties, 306 physiological properties, 69, 71, 304, 305 precautions, 305, 306 vapour pressure, 305 Suppression, 135 Surface area effects, 50, 199 Symbols for dangerous substances, 446, 452 Synthetic lubricants, 159 Synthetic resins, 172 Systemic poisons, 19, 77... 

Number of plates = total heat transfer area / effective area of one plate = 72.92/0.75 = 97... 

Surface area effect on the relaxation time constant In a previous communication (17) we have developed a simple dynamic model which allows one to predict the change in the mole number of silver oxide S Ac, therefore AV, in terms of the imposed current, Pq and The dynamic equation of the model was... 

Heat detectors should be spaced to ensure prompt detection of heat given off by incipient fire conditions. Spacing considerations should include the degree of hazard, type of detector used, geometry of the protected area, effects of air handling equipment if it is indoors, or environmental factors (wind, temperature, etc.) if it is outdoors. See NFPA 72 for more information on spacing and installation requirements. 

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