EFFECT OF AIR CARBON ARC GOUGING AND SUBMERGED ARC WELDING ON THE ELECTROCHEMICAL PROPERTIES OF AISI 316L AND 321 STAINLESS STEELS

The paper aims to evaluate the use of air carbon arc gouging-ACAG followed by submerged arc welding-SAW to repair two types of austenitic stainless steels, AISI 316L and AISI 321, verifying the effects on the resulting electrochemical properties: degree of sensitization and susceptibility to intergranular corrosion. The weld grooves of the 19,05 mm thick plate were prepared by machining (V-shape, with 2 mm weld root face thickness) and processed by SAW. Aiming at to simulate a repair operation a gouged groove (~6-7mm deep) was produced on the top of the weld metal, close to the Thermally Affected Zone by ACAG and rewelded by SAW. The welded joints were studied in three different situations regarding the joint preparation treatment after gouging, namely: i) without any type of cleaning, ii) brushing and iii) rectifying. The degree of sensitization of the welded joint was evaluated using the double loop potentiokinetic reactivation (DL-EPR) technique according to ISO 12732 Corrosion of metals and alloys — Electrochemical potentiokinetic reactivation measurement using the double loop method (based on Cihal's method), and susceptibility to intergranular corrosion in accordance with ASTM A262-15 Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels, Practice A. The results showed that the ACAG procedure does not affect the corrosion resistance of the steels studied even if no cleaning procedure was used to eliminate the contaminants left in the gouged groove surface. Therefore, the use of the gouging process presents an interesting alternative to repair welding in the field as well as to remove defect root pass and guarantee full penetration of the weld. Besides higher material removal yield, less effort from the operator, low cost, and ease of use in the field are attractive advantages of the technique.