Another successful application is described in this article of the rapidly expanding technique of anodic protection. This report deals with kraft digesters in pulp and paper manufacturing.
In the manufacture of sulfate or kraft paper products, the first stage is reduction of wood chips to a pulp cellulose fibers. This is accomplished by cooking the chips in a large steel digester at a temperature of 350˚F for about three hours, in a liquor containing 100 grams per liter sodium hydroxide and 35 grams per liter sodium sulfide. The liquor is very caustic and corrosive.
Digesters are vertical, cylindrical vessels of mild steel with conical bottoms. They are about 50 feet high and 10 feet in diameter with a wall of thickness of 1½ to 2 inches.