Effect of pH in the Range 6.6–14.0+ On the Aerobic Corrosion Fatigue of Steel

Abstract

The aerobic corrosion fatigue performance of a normalized AISI 1036 steel was determined in a 3 percent NaCl brine of various pH levels from 6.6 to the saturated caustic level (14+). A systematic behavior was observed, a behavior which is believed typical for similar steels. These statistical test findings are summarized in fatigue curve form, and in addition, several special corrosion phenomena are recorded. The principal results are explicable in terms of ferrous hydroxide solubility and oxygen concentration cell behavior as the two primary variables. The oxygen concentration cell system is considered as a pH-sensitive discontinuity to the transformed ferrous hydroxide films. A theory is outlined to explain the principal points observed. Finally, control measure possibilities are suggested. 3.4.7

Corrosion Fatigue of Steel in Various Aqueous Environments

“…Permeation rates increase with sulphur content of the steel in the range 0.002-0.24% S but only where the H,S supply can be maintained by dissolution of inclusions [15]. Several investigators [2, 18,191 believe that the increased corrosion fatigue degradation of high strength steels is related to their sensitivity to hydrogen embrittlement.…”

“…Measurements of hydrogen permeation rates through cathodically polarized mild steel containing (FeMn)S inclusions show that H2S produced at the metal surface by dissolution of inclusions promotes hydrogen entry into steels. Permeation rates increase with sulphur content of the steel in the range 0.002-0.24% S but only where the H,S supply can be maintained by dissolution of inclusions [15]. Several investigators [2, 18,191 believe that the increased corrosion fatigue degradation of high strength steels is related to their sensitivity to hydrogen embrittlement.…”