METAL DUSTING CORROSION OF HIGH TEMPERATURE EQUIPMENT

摘要

Metal dusting corrosion is the catastrophic carburisation of a metal operating at high temperatures, and gas compositions with carbon activities greater than 1 and has been found to occur in a number of industries, notably, refining, heat treatment and direct reduction iron plants. This form of corrosion results in the formation of fine particles of metal and carbon, which are easily removed as a fine dust under conditions of high flow. If left unchecked, this form of attack can lead to a serious reduction in the wall thickness of equipment, and if operating at pressure, can seriously affect the integrity of the equipment and the safety of the personnel. This paper will discuss the mechanisms of metal dusting, the thermodynamic conditions under which it occurs and the kinetics of the gas/solid reactions which occur. Based on these theoretical concepts a number of factors can be altered to improve a components resistance to metal dusting attack, these being: change of alloy composition, modification of the metal surface to act as a barrier to attack, as well as the addition of an inhibitor to the process stream. All the items discussed will be illustrated by means of practical examples of plant affected by this form of corrosion.