EFFECT OF HYDRODYNAMICS ON PITTING

Studies were made with an artificial pit in the side of a flow channel to determine quantitative hydrodynamic effects on pitting rate. Experiments were conducted under potentiostatic conditions with iron, titanium, and aluminum in chloride, bromide, and iodide solutions. Two modes of pitting were observed: (1) a high current density limited only by ohmic resistance in solution, and (2) a lower current density limited by mass transfer. The mass transfer limited current density increased with flow rate, but was not always well defined because solid corrosion products in the pit disturbed the solution flow pattern.