Corrosion Testing in Digester Liquors, 1996 Engineering Conference Proceedings

A new technique is described for assessing the corrosivity of digester liquors, and for evaluating the optimum means for corrosion protection in individual digesters. Specimens of carbon steels, weld overlays, and thermal spray coatings were exposed in autoclaves containing actual digester liquors, at the cooking temperature (170°C), under conditions of potentiostatic polarization. Low-silicon SA285-Grade C “Mod” carbon steel was found to have superior corrosion resistance to the SA516-Grade 70 carbon steel. Automatic gas metal arc weld overlays were found to have superior corrosion resistance to manual shielded metal arc weld overlays of comparable chromium content. ER312 stainless steel weld overlays were found to be slightly more corrosion resistant than ER3093LSi stainless steel weld overlays, likely due to higher chromium content of the ER312. Inherently high porosity twin wire arc spray coatings experienced greater liquor penetration than low porosity high velocity oxygen fuel coatings or essentially non-porous combustion arc spray coatings.