Retarding corrosion during the concn. of sulphuric acid - by using plant made of nickel-iron-chromium-molybdenum alloy

摘要

The aq. H2SO4 solns. have a concn. of 20-80 wt.% and also contain min. 0.02 wt.% ferric ions, and the concn. of carried out in appts. or plant made of an alloy contg. by wt. 15-30% Cr, 10-60% Ni, 1-10% Mo opt. with the following, all maxima 5% Cu, 1.5% Ti, 0.5% Si, 1% Mn, 0.5% C, the remainder being iron. The pref. aq. acid solns. contain 0.02-0.15% ferric irons, or 0.1-1% ferric ions, in either case added as such, or added as ferrous ions plus air or O2 or another oxidant, viz. HNO3, N2O3, KMnO4, or ch romate ions. The amt. of ferric ions, and thus the corrosion rate, is pref. controlled by measuring the electrochemical potential:-metal/soln.