The effect of a nickel alloy coating on the corrosion of furnace wall tubes in a waste wood fired power plant

Abstract

The use of waste wood as a fuel in power plants is becoming more widespread in Europe, because it is a renewable energy source with a lower cost than forest fuel. However it is more corrosive than coal and corrosion problems have arisen in the furnace wall area of a low NOx heat and power boiler. The furnace walls are made of a low alloy steel which has been coated in some parts with a nickel alloy to reduce corrosion. In this work, furnace tubes coated with a nickel alloy were compared to the uncoated tubes of the low alloy steel 16Mo3 after 3 years of exposure in the boiler. The nickel alloy coating and uncoated material were also compared with more controlled testing on a corrosion probe lasting for about 6 weeks. The corrosion rates were measured and the samples were chemically analysed by SEM/EDS/WDS and XRD methods. The corrosive environment was also modelled with Thermo‐Calc software. The corrosion rates measured from the probe and tube samples of 16Mo3 agreed well with each other, implying linear corrosion rates. The results also showed that the use of nickel alloy coatings changes the corrosion mechanism, which leads to a dramatic reduction in the corrosion rate. The results are discussed in terms of the corrosion mechanisms and thermodynamic stability of the corrosion products.

Field exposure of FeCrAl model alloys in a waste‐fired boiler at 600°C: The influence of Cr and Si on the corrosion behaviour

“…The reference material used was a 16Mo3 sample ring, overwelded with Inconel 625. This has been exposed various times in similar field exposures (biomass‐ and waste‐fired boilers) due to its exceptionally high corrosion resistance and can therefore be used as a measure of the corrosivity of the present conditions. A disadvantage with the overweld is that the sample ring thickness is not even and accurate thickness measurements for calculation of material loss was therefore not possible.…”

Effect of water vapour partial pressure on the chromia (Cr2O3)-based scale stability

“…[1][2][3][4][5][6][7][8] One method to increase the steam oxidation resistance of the alloy structural components is to modify the composition to form a protective external Cr2O3-based scale. [9][10][11][12] It is well-known that increasing an alloy Cr-content can enhance the formation of a protective external Cr2O3-based scale.…”

The influence of NaCl and CaCl2 induced high temperature corrosion on the aqueous corrosion resistance of stainless steels

“…Abels et al have shown, that at high temperatures Cl 2 acts more corrosive to metallic materials than HCl. However, both species are able to form volatile metal chlorides and oxychlorides with metal oxides or with metallic elements of the bulk alloy . The generation of metal chlorides requires the supply of the oxide/metal interface with chloride‐bearing educts.…”