Application of GDOS (glow discharge optical spectroscopy) and SIMS to the analysis of surface corrosion products on stainless steel after exposure to liquid alkali metals

Abstract

Corrosion of steels by liquid alkali metals involves the transfer of non metals, such as C, N or 0, from solution in the alkali metal to the surface of the steel. Surface corrosion products may then be formed. With oxygen in sodium these products may be ternary oxides, with nitrogen in lithium the ternary nitride Li9CrNS is formed and with carbon binary carbides are formed in both alkalies. Along with the surface corrosion products, element depletions and carbon or nitrogen diffusion profiles are created. The analyses of thin corrosion product layers and the determination of the concentration profiles of carbon and nitrogen are important requirements for the understanding of the corrosion process. Lithium penetration into steel is also a major problem in lithium corrosion. Lithium is extremely difficult to determine by conventional analytical methods, due to its low atomic number. In this paper the use of glow discharge optical spectroscopy (GDOS) and SIMS for the study of surface corrosion products, is described, together with a quantitative determination of the carbon-depth profile in type 316 steel exposed to liquid sodium.

Electro-chemical behaviour of different metals in Sodium Chloride solution

“…The surface of metals like iron, chromium,AISI type 446 stainless steel and other metals are analysed under the influence of H 2 S / N 2 gas mixture flow at elevated temperatures, and infrared reflectance and Raman spectra was observed on iron,chromium and stainless steel at elevated temperatures, where high temperatures in surrounding media also influence s the corrosion rate of metals [1,2,3,5]. The method of fabrication of material specimen and its surface roughness also plays a role.When stainless steel metal is exposed to various liquids in most of the industrial applications, and to study the effect of corrosion rate and to determine the quantity of carbon depth profile,the Glow Discharge Optical Spectroscopy(GDOS)and Secondaryion mass spectrometry (SIMS) technique are used [4].…”

“…The American Society of Testing of Metals -ASTM: G -59 -97 (2014) standard describes about the method of conducting a photodynamic polarization measurement by using potentiostat equipment using two and three reference electrodes, electrochemical cells etc., In this test methods, a small potential is applied to find the corrosion rate potential (E corr ) and current density (i corr ) by experimentation. The corrosion rate of metal depends on several factors like time duration of exposure, depending upon surrounding atmospheric conditions, type of media, Temperature of media, material density and surface area of exposure [1,2,3,5]. Several preventive measures are taken to control corrosion rate like coating the metals with paints, non-corrosive metal coatingsetc.…”