This paper aims to focus on the effects of temperature of the immersion media on the corrosion behaviour of differently heat‐treated X20Cr13 stainless steel.
Abstract
Purpose
This paper aims to focus on the effects of temperature of the immersion media on the corrosion behaviour of differently heat‐treated X20Cr13 stainless steel.
Design/methodology/approach
Specimens, quenched on air, quenched in oil and quenched in oil and then tempered, were tested during exposure in 0.1 M H2SO4 at 30, 40 and 50°C. The results were interpreted on the base of potentiodynamic and impedance measurements.
Findings
From the impedance spectra a reaction mechanism can be determined: after samples had reached and passed the active peak, expressed as the highest peak on the potentiodynamic curve, corrosion products at interfaces, which were adsorbed at metal surface, led to an increase in the charge transfer resistance. Elevated temperature of immersion media has had appreciable influence on the corrosion rate and adsorption of products, but at this temperature level did not affect the principle of corrosion reactions. Activation energies were calculated to exhibit temperature dependence of current density, which was the highest for the oil‐ and the lowest for the air‐quenched sample.
Originality/value
The paper provides further research on stainless steel, the corrosion behaviour of which can be controlled already by heat treatment.
Details
Keywords
M. Slemnik and D. Pečar
The purpose of this paper is to present a study of corrosion properties of the highly corrosion‐resistant stainless steel Prokron 11Nb, which is suitable for use in…
Abstract
Purpose
The purpose of this paper is to present a study of corrosion properties of the highly corrosion‐resistant stainless steel Prokron 11Nb, which is suitable for use in high‐temperature and high‐pressure systems.
Design/methodology/approach
Prokron 11Nb was immersed in 0.1 M H2SO4 that had been previously sparged with CO2 and was exposed to high pressures within the range of 1‐300 bar at a constant temperature of 25°C. Treated surfaces were scanned with an electronic microscope (scanning electron microscope) equipped with energy spectrum distribution (energy dispersive spectroscopy) to analyze the morphologies and compositions of surface deposits. Corrosion properties were measured using the potentiodynamic method and electrochemical impedance spectroscopy.
Findings
The corrosion rate decreased with increasing CO2 pressure, which accelerated surface passivity, but only up to a pressure of 200 bar. Higher pressures (300 bar) increased the corrosion rate. The trends in corrosion rate with CO2 pressure agree with the stability of a protective layer where iron carbonate is present.
Originality/value
A high‐pressure CO2 treatment at low temperature is found to be a useful method for improving the passivity of stainless steel. Iron carbonate, which is the result of CO2 corrosion, forms a stable protective layer on the steel surface and this lowers the corrosion rate.