Corrosion and protection of kraft digesters

The mechanisms of corrosion and cracking in kraft digesters are reviewed, including stress corrosion cracking, general corrosion, pitting, preferential weld attack, and intergranular corrosion. Also discussed are the various corrosion protection measures, including corrosion-resisting weld overlay, thermal spray coating, and anodic protection. In situ corrosion monitoring by coupons, corrosion potential probes, and linear polarization probes is described, as well as laboratory autoclave testing in digester extraction liquors. Application : digester owner/operators will be better informed as to the kinds of corrosion testing required to ensure selection of the best methods of corrosion protection for their digesters.