The stability of high temperature materials in reducing highly carbonaceous atmospheres in
the temperature range of 400 to 800°C can be raised with the help of a nickel-tin coating.
Coking and metal dusting are dependent on the catalytic activation of the carbonaceous
gas species by the material surface components iron, cobalt and/or nickel. If the access to
the catalytic active metal centers is impeded for the gas species, the primary condition for
the metal dusting attack — atomic carbon — is not available. The dissociation of e.g.
carbon monoxide is suppressed on nickel-tin surfaces. Initial tests with a nickel-tin coating
on low alloy steel have shown an improved behavior under metal dusting conditions up to at
least 3000 hrs. Following these initial tests the coating was applied to several conventional
materials including low alloy steel, ferritic and austenitic high alloy steel and nickel base
alloys. Test coupons were exposed under metal dusting conditions at 620°C for several
hundred hours and evaluated via metallographic and microprobe analyses. Alloy
parameters influencing the effectiveness and resistance of the coating were identified.
Keywords: metal dusting, coking, nickel-tin, surface poisoning