Lead alloys corrosion behaviour

Table 2.4. Corrosion behaviour of cast lead-calcium alloys with various amounts of tin. (Corrosion rate mils per year at 0.84mAcm . )...

Malkow ft al. systematically investigated the thermal expansion and corrosion behaviour of commercial steels and model alloys [53]. The thermal expansion coefficient of ferritic steels decreases with increasing Cr content up to 20 wt% and increases with increasing Al content. By such alloying, the thermal expansion of ferritic steels can be adjusted and matched to the Ni/YSZ anode substrate, but not to the YSZ electrolyte. The oxidation of steels depends not only on the Cr content, but also on small amounts of alloyed elements, especially Al and Si. Once a compositional threshold is reached, alumina and silica layers arc formed instead of a chromia layer. This leads to a reduction in oxidation rate. However, such alumina and silica layers are insulating and have to be avoided when the steel interconnect is in contact with a contact or electrode material. In a comparative study [54] of commercially available ferritic steels with chromium contents between 12 and 28%. the contact resistance against... 

As copper is not an inherently reactive element, it is not surprising that the rate of corrosion, even if unhindered by films of insoluble corrosion products, is usually low. Nevertheless, although the breakdown of a protective oxide film on copper is not likely to lead to such rapid attack as with a more reactive metal such as, say, aluminium, in practice the good behaviour of copper (and more particularly of some of its alloys) often depends to a considerable extent on the maintenance of a protective film of oxide or other insoluble corrosion product. 

Pressurised water nuclear reactors require metals that will have a high degree of corrosion resistance to pure water at around 300°C. Laboratory testing of materials for this application have included potentiostatic polarisation experiments designed to clarify the active-passive behaviour of alloys as well as to establish corrosion rates. Since pressure vessels are used for this work, it is necessary to provide sealed insulated leads through the autoclave head . 

Nitric acid reacts energetically at ordinary temperatures, with formation of the nitrate and of the oxides of nitrogen. The behaviour of the metal with hydrochloric acid is similar to that of lead. The action of concentrated sulphuric acid and of nitric acid finds application in the separation of alloys of gold and silver. The corrosive effect of acids is accelerated by the presence of an oxidizer.5... 

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