Uhlig report

Another contribution of the potentiostatic technique to s.c.c. studies has been the report that cracking prevails essentially at two potential levels for metals showing an active-passive transition. These potentials are located near the top and bottom of the passive region. Along the same lines, Uhlig and his co-workers have determined critical ranges of potential for s.c.c. , although their theoretical interpretation differs from that of the other references cited. 

Based on the proposed theory, the values of AGf 0 (and Aohydrophilic ions (NHj, Mg2+, Sr2+, Ni2+, Fe2+, Fe3+, C10] BrO(, CN , I03, IIC03, NO2, OH-), whose AG i1 ° w values have been reported, but their hydration numbers are unknown. In the predictions, the first decision on whether the ion is hydrated in NB is made by means of (z/r) as described above, if (z/r) > 5 (r in nm) for a cation or (z/r) < —4 for an anion (except polyanions), the ion should be hydrated in NB to a certain extent. For these hydrated ions, the hydration number and the hydrated radius are evaluated. Then the charge-independent and -dependent terms of AG i1 ° w are calculated using the Uhlig formula and the empirical equation, respectively. Finally, the summation of the two terms yields the total value of AG ° W. 

The 1973 estimate of A 470 million was noted to be about double the 1955 estimate of 240 million made by Worner (8) and was further compared with an estimate of the annual cost of corrosion to Australia of 900 million published in 1972 by E.C. Potter in 1972. Potter (9) used a published estimate of corrosion costs to Great Britain (2) equal to 3.5% of GNP and included corrections relevant to Australia to arrive at A 900 million corrosion costs. Potter s cost estimate is higher than that of Revie and Uhlig because some elements for the indirect costs of corrosion were included in the Potter report. 

A survey on the cost of corrosion was conducted in 1977 and a report was published by the Committee on Corrosion and Protection (4). The annual cost of corrosion to Japan was 2.5 trillion yen (US 9.2 billion) in 1974. The GNP of Japan in 1974 was 136 trillion yen, and the cost of corrosion was 1-2% of Japan s GNP for 1974. This cost is a direct cost. Indirect costs would be much higher. Japan s committee estimated the cost of corrosion by (i) corrosion protection products and services and (ii) corrosion cost by industry sector. The Uhlig method determined the costs primarily on the basis of the cost of corrosion protection products and services such as coatings, inhibitors, corrosion-resistant materials, and cathodic protection. The... 

The separate and combined effects of aeration, agitation, and carbon dioxide have been investigated in the laboratory on a number of occasions. Bengough and Hudson (1919), Kenworthy and Smith (1944), Bauer and Schikorr (1934), and Anderson and Reinhard in the Corrosion Handbook (Uhlig, 1948) have reported on the effect of these factors on the corrosion of zinc at room temperature. Agitation, whether by movement of the water or the specimen, or by bubbling air or carbon dioxide through the water, tends to increase corrosion. 

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