Evaluation of Alloy 146, 279, 900, and 926 sensitization to intergranular corrosion by means of electrochemical methods and image analysis

Application of Confocal Laser Scanning Microscopy to the In-situ and Ex-situ Study of Corrosion Processes

“…Fig. 5 shows two images obtained by scanning electron microscopy (SEM) of a duplex stainless steel (DSS), Alloy 900, before and after heat treatment at 825 ºC in an inert atmosphere for 1 hour (Leiva- García et al, 2009). In this image it can be observed how after heat treatment new phases appear and the percentage of one of the initial phases (ferrite) decreases.…”

In Situ Study of Corrosion Evolution of Alloy 926 (UNS N08926) in its Unsensitized and Sensitized State in LiBr Solutions Using Confocal Laser Scanning Microscopy

“…Heat treatments were carried out at 825 ºC for a period of 1 hour. These conditions were selected because in previous works, sensitisation was observed with this heat treatment (29,30). The electrode was covered with an epoxy-resin; in this way only a circular area of 1.6 mm in diameter was exposed to the LiBr solution (the area of the electrodes was determined for every test by image analysis).…”

Study of the sensitisation of a highly alloyed austenitic stainless steel, Alloy 926 (UNS N08926), by means of scanning electrochemical microscopy

“…When austenitic stainless steels are incorrectly heat treated, in the temperature range between 500 and 900 ºC, chromium and carbon combine at the grain boundaries to form chromium carbides (typically Cr 23 C 6 ), whilst simultaneously as these carbides form, chromium depletion occurs at the adjacent zones. This process is called sensitisation and leads to a decrease in the corrosion resistance of stainless steels, notably resistance to intergranular corrosion, being due to the depleted regions becoming anodic in the presence of an electrolyte [3][4][5][6][7][8][9][10].…”

“…These conditions were selected based upon a previous study [9]. After heat treatment, an electrical connection was made to the specimen in order to allow electrochemical measurements to be made.…”

“…Conventional electrochemical techniques, such as electrochemical reactivation tests or cyclic potentiodynamic curves, have been widely used to study sensitisation and provide important information about the sensitisation processes [4,[6][7][8][9][10][12][13][14][15][16][17]. Recent advances in the field of localised microelectrochemical techniques have provided the facility to acquire spatially resolved information about the corrosion processes occurring on the surface of the metal.…”