EFFECT OF SILICATE AND PHOSPHATE ON THE FATIGUE CRACK GROWTH RATES IN TYPE 403 STAINLESS STEEL IN CONCENTRATED SODIUM CHLORIDE AND SODIUM HYDROXIDE SOLUTIONS.

Corrosion fatigue crack growth rates of quenched and tempered Type 403 stainless steel have been measured in solutions with and without the addition of sodium silicate and sodium phosphate as inhibitors. All tests were performed at 100 degree C with a sinusoidal loading wave form at R equals 0. 5 and at frequencies of 0. 1, 1, and 10 Hz. Tests in air were also conducted to obtain fatigue crack growth rates. At open circuit potentials, crack propagation rates were highest in concentrated sodium chloride. Environmental enhancement became more evident as frequency was decreased in both 10 mol kg** minus **1(m) sodium hydroxide and saturated (6. 6 mol kg ** minus **1) sodium chloride solutions. Sodium phosphate and sodium silicate showed no beneficial effect in 10 mol kg** minus **1 NaOH solution. Both showed inhibiting effects in 6 mol kg** minus **1 sodium chloride solution.