218 RELATIVE ELECTRO-CHEMICAL POSITIONS OF WROUGHT IKON, ETC. 



Ill experiments made by the author to ascertain the galvanic action taking 

 place between wrought iron and steels, &c, over more extended periods of 

 time, it was found that galvanic action between these metals had a tendency 

 to be reduced from various causes during prolonged exposure to sea-water and 

 other solutions. 



The general deductions from the foregoing observations are that — 



1st, The electro-chemical position of wrought-iron, steels, and cast metal 

 appears capable of changing according to the nature of the solution in which 

 they are immersed, an acid solution producing frequently different results from 

 one containing only neutral salts, This interchange of electro-chemical position 

 between the metals being also frequently observable both when immersed in 

 an acid and neutral solution, as indicated by the preceding tables. 



2nd, A measurable difference is noticeable in the behaviour of the various 

 steels, &c. employed under the conditions recorded in the experiments. This 

 would lead to the conclusion that the danger from the greatly increased 

 corrosion in sea-water, &c, through galvanic action, is a factor not to be 

 disregarded in compound structures of the preceding metals. The tendency to 

 polarise each other's action, and the consequent interchange of electro-chemical 

 position, would appear to exert a considerable influence in retarding and 

 reducing this source of danger. Galvanic action between wrought iron and 

 steels, &c, appears (from experiments on hand by the author) also to be 

 materially reduced in course of extended periods of time, otherwise the liability 

 to destructive corrosion through such action, though never inconsiderable, 

 would be a more formidable matter to encounter than in engineering practice 

 it really is. At the same time, it need scarce be remarked, this source of dis- 

 integration should not be overlooked in constructive works of wrought and 

 cast iron and steel. 



It is not now necessary for the author to attempt to enter into the further 

 practical application of the results deducible from the experiments contained in 

 this memoir ; he has, however, great pleasure in being permitted the honour 

 to present the results herein recorded as a contribution to the chemistry of 

 iron and steel. 





