THE PHILIPPINE 
JOURNAL OF SCIENCE 
VOL. 16 MAY, 1920 No. 5 
CORROSION OF IRON IN SULPHURIC ACID. EFFECT 
OF CHROMIUM COMPOUNDS! 
By GeorGeE W. HEISE and AMANDO CLEMENTE 
Of the Bureau of Science, Manila 
ONE TEXT FIGURE 
The use of passivifying agents in inhibiting the corrosion 
of iron is, of course, well known. Thus, the addition of potas- 
sium dichromate to water has been suggested as a means of 
preventing boiler corrosion.’ 
Under certain conditions, however, substances that ordinarily 
passivify may increase the rate of corrosion. For example, the 
rate of corrosion of iron in a salt solution is accelerated by 
the addition of potassium dichromate because, according to 
Friend,* a reaction occurs whereby free acid is formed, as 
follows: : 
H,O + K,Cr,0, + 2NaCl = K,CrO, + Na,CrO, + 2HC1l. 
Tn the presence of free acid, potassium dichromate acts as a 
depolarizer, removing hydrogen, and thus facilitates the dis- 
solution of the iron. The accelerated corrosion of iron in sul- 
phuric acid in the presence of potassium chromate and dichromate 
was determined experimentally by Watts* who reported as 
follows: 
The great increase in corrosion caused by the addition of potassium 
chromate was therefore rather surprising. A comparison * * * sug- 
‘Received for publication, February 27, 1918. 
*Cushman, A. S., Bull. U. S. Dept. Agr. 30 (1907). 
* Friend, J. N., Journ. Iron and Steel Inst. 2 (1908) 9, quoted by Friend, 
J. N., Corrosion of Iron and Steel. Longmans, Green & Co. (1911) 163. 
‘Watts, O. P., The effect of various substances on the rate of corrosion 
of iron by sulphuric acid, Trans. Am. Electrochem. Soc. 21 (1912) 337-353. 
171114 439 
