Effect of the Addition of Silicon on Corrosion-resistivities of 18% Cr-8% Ni and 18% Cr-14% Ni Types Stainless Steels in Boiling Acid Solutions

Abstract

The corrosion tests were carried out on stainless steels of 18% Cr-8% Ni and 18% Cr-14% Ni types containing 0.5 to 2.5% Si. The corrosives were aqueous solutions of 1, 5, 10 and 20% H₂SO₄, 5% HCl and mixtures of H₂SO₄ and HNO₃ in boiling conditions.
The specimens were annealed at 840° for 2 hours or quenched in water after heating at 1090° for 30 minutes.
The effective quantities of silicon were as follows: On 18% Cr-8% Ni types, in both cases of quenching and annealing, they were 0.5% and 2% Si against 5%, 10% and 20% sulphuric acid.
On 18% Cr-14% Ni types, in both cases of quenching and annealing, they were 0.5 to 2% Si against 5%, 10% and 20% sulphuric and 5% hydrochloric acid and 2.5% Si, in only case of quenching, against mixed acid.