222 SUMMARY OF CURRENT RESEARCHES. 



Influence of Carbon on the Corrodibility of Iron.* — In the course 

 of an investigation upon the corrodibility of six pure carbon-steels con- 

 taining 0*1 to • 96 p.c. carbon, C. Chappell has microscopically examined 

 polished specimens at successive stages of corrosion by immersion in sea- 

 water. The oxides were removed by rubbing on selvyt cloth. The first 

 feature in the process of corrosion was the appearance of numerous dark 

 spots due to the action of the manganese sulphide. The corrosion of 

 the pearlite areas, faintly visible after about two hours immersion, rapidly 

 increased in vigour, and spread to the ferrite. Selective corrosion of 

 various ferrite crystals set in at a later stage, other ferrite crystals re- 

 maining comparatively unaffected. It is suggested that the difference 

 in the rate of corrosion of different ferrite crystals is due to the diffe- 

 rent relationship of the exposed surfaces to the crystallographic axes. 

 The development of sharply defined geometrical pits was a marked 

 feature of the corrosion of the ferrite ; in any one crystal the pits were 

 identical in form. 



* Journ. Iron and Steel Inst., Ixxxv. (1912, 1) pp. 270-96 (14 figs.). 



