EFFECT OF PLATINUM ELEMENTS ADDITIONS ON THE ACTIVE DISSOLUTION OF PLASTIC CHROMIUM IN SULFURIC-ACID

Alloys with 0. 1 to 0. 4 mass % Ru, Pd, Ir, or Pt were investigated in 40% sulfuric acid in active state under cathodic polarization ( minus 0. 175 v). All additions are responsible for reduced anodic dissolution. Two mechanisms decelerating active dissolution of the cathode-modified chromium are blocking mechanism (cathodic component atoms block the active points in the lattice) and screening mechanism (cathodic component, while being crystallized on the surface, partly screens the latter).