• Gsellmann, Bernadette
• Vallant, Rudolf
• Sommitsch, Christof
• Venkata, Ranganada Kasyap Pradeep Godavarthy Anantha

Abstract

Tinting colours are a problem often arising at the welding root surface of stainless steel pipes. They appear if a certain residual oxygen content is in the reducing N2/H2 purge gas. Different tinting colours are directly connectable to the thickness and the degradation of the chromium oxide layer. For the artificially produced different tinting colours in air, the reduction of the corrosion resistance is evaluated, to determine the critical residual oxygen content. The tinting colours show a change of the corrosion potentials. The investigations are conducted on the most common stainless steel type AISI 304 / 1.4301 of surface conditions 2B (Skin Pass) and 2R (Bright Annealed) with different tinting colours, artificially produced, using a furnace. Electrochemical linear polarization tests are performed on the tinted samples to investigate their corrosion resistance as a function of the Open Circuit Potential (OCP) and the Break Through Potential (BTP). Therefor a standard three electrode set up in a 1l corrosion cell with a 5% NaCl electrolyte is used. Furthermore, the investigations are aimed to standardize the corrosion testing procedure and parameter finding for future corrosion investigations on stainless steels for different applications depending on their surface condition. After the electrochemical tests the severity of the corrosion attack is evaluated metallographically by measuring the depth and the diameter of the pits.

Topics

• impedance spectroscopy
• surface
• stainless steel
• chromium
• Oxygen
• pitting corrosion
• positron annihilation lifetime spectroscopy
• Photoacoustic spectroscopy
• oxygen content