Premium
Special aspects of localized High‐temperature corrosion
Author(s) -
Heubner Ulrich,
Hofmann Franz
Publication year - 1989
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19890400603
Subject(s) - corrosion , metallurgy , materials science , sulfidation , alloy , grain boundary , high temperature corrosion , intergranular corrosion , pitting corrosion , stress corrosion cracking , combustion , cracking , coal , composite material , microstructure , sulfur , chemistry , organic chemistry
As in aqueous corrosion a localized corrosive attack can be important in high‐temperature corrosion of metallic materials and become, unvoluntarily, a lifetime determining factor for combustion systems. Deposit‐induced corrosion is the most important form of localized corrosion on alloy 800 and other materials in advanced coal combustion systems. Coal‐ash deposits may cause a sulfidation/oxidation reaction which propagates preferentially along grain boundaries into the underlying metallic material. Preferred grain boundary corrosion may also occur in the walls of the fuel nozzle tubes of gas combustion systems. In this case, an oxidation reaction takes place. The lifetime of the tubes can be increased by use of a special alloy 601 H grade. Pitting may be observed in coal combustion systems. It has also been observed on alloy 601 after service in ceramic firing kilns where it is promoted by the presence of chlorine. Additionally, pitting occurs under carburizing conditions (metal dusting) as does cracking being similar in appearance to stress corrosion cracking in aqueous corrosion. Compared to deposit‐induced and grain boundary corrosion, crevice corrosion is of minor importance in high‐temperature corrosion. Only one example has been identified so far on alloy 600 but which may also be interpreted as a kind of deposit‐induced corrosion.