Characteristics of the deposits and oxide films formed on 316L stainless steel in situ tested on a boiler of 1000 MW pulverized coal‐fired power plant for 150 h were examined. The results show that the deposits are mainly composed of outer fly ash, middle sulfate, and chloride and fluoride in the inner layer. Oxide films are mainly Fe2O3 and Fe3O4. Two models of coupling mechanism of dew point corrosion and viscous ash deposits at different temperature ranges are proposed to instruct engineering application.

The high-temperature corrosion characteristic of 0Cr18Ni9NbCu3BN steel was analysed in this paper. The samples were selected from a super-heater with service time of 34 696 h in an ultrasupercritical boiler in China. Scanning electron microscopy, energy spectrum analysis and energy dispersive X-ray spectroscopy were adopted to analyse the element constitute, morphology and phase structure of the corrosion scale. The results indicated that corrosion scale can be divided into three layers, and the middle layer of corrosion scale is enriched with Cr. The Cr-rich layer could not set an efficient barrier to prevent sulphur from penetrating to the matrix. It actually can prevent O from penetrating to metal base effectively. The main corrosion forms are high-temperature oxidation and sulphidation, while the sulphidation rate was greater than the oxidation rate. The sulphidation is the major type of corrosion attack. Oxidation and sulphidation interactively cause the corrosion progress consistently.

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