SURFACE STATE EFFECT OF WELDED STAINLESS STEELS ON CORROSION BEHAVIOR

Abstract

<p style="margin: 2pt 0cm; line-height: 12.5pt;"><span style="font-family: 'Times New Roman','serif'; mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small;"><span style="color: #585858;">Welding joints of stainless steels are in practice very sensitive places attacked by local corrosion, such as pitting and crevice corrosion, mostly in chloride containing oxidizing environments. It is caused by different oxidation products created on the surface by welding. Corrosion resistance of stainless steels is affected by quality of passive layer (Cr₂</span></span><span style="color: #585858; font-size: small;">O</span>_{<span style="color: #585858; font-size: small;">3</span>}<span style="color: #585858; font-size: small;">) which created at normal conditions on air. After welding the steels are heated and on the surface are originated different types of oxides which do not have the same protective properties. Resistance to </span><span style="letter-spacing: -0.2pt;"><span style="color: #585858; font-size: small;">intergranular</span></span><span style="color: #585858; font-size: small;"> and pitting corrosion of the welded stainless steels with different surface finishing was tested. Experimental materials are the austenitic stainless steel AISI 316L (welded by the TIG method in inert argon atmosphere with filler) and the ferritic stainless steel AISI CA6-NM (welded by the WPS method in inert argon atmosphere with filler and after welding heat treated). Character of the surface after welding and after finishing by grinding and pickling was evaluated by SEM microscopy, EDX analysis. Corrosion resistance to local forms of corrosion was investigated by electrochemical potentiodynamic test and by exposure tests in chloride solutions. The steel AISI CA6-NM was tested in fluvial water to simulate real operation environment. The evaluation is supported by microscopic analysis. Susceptibility to intergranular corrosion was tested too and results detect the dangerous localities for corrosion attack and show increasing of corrosion resistance by surface treatment. </span></span></p>