Patent Number: 059404647
Section: description

FIGS. 1 and 2 indicate that there is no significant enhancement of the resistance to corrosion in lithium containing water beyond about 0.6% Sn and 0.2% Fe. FIGS. 3 and 4 show there is an interest in an iron content higher than 0.2%, for enhancing the resistance to corrosion in water steam at 400.degree. C. and 415.degree. C. and reducing the undesirable effect of a high Sn content. Such Figures also indicate that the favorable results which are found for an alloy according to the invention are lost if there is a low tin content or no tin. Last, FIG. 5 indicates that there is a progressive loss of the resistance to nodular corrosion when the tin content increases, without significant improvement of the characteristics by adding iron. FIG. 5 shows that beyond a tin content of 0.6%, corrosion became faster and it also shows that, for an acceptable tin content, corrosion is faster if the iron content increases beyond about 0.3%. From a general consideration of all results, a composition range which is favorable regarding corrosion is defined by the three curves indicated in FIG. 6. Curve A limits a zone of interest as regards resistance in water at 360.degree. C. with a 70 ppm lithium content i.e. under conditions which are more severe than those which prevail in a reactor, as regards the lithium content. Curve B limits a zone in which there is satisfactory resistance in lithium containing steam at a temperature slightly beyond 400.degree. C. Last, curve C approximately corresponds to a limit of the acceptable contents as regards nodular corrosion resistance, in water steam at 500.degree. C. It is however possible to exceed the above indicated zone when some types of corrosion are not likely to occur.