Abstract:
Cr3C2–NiCr coatings were sprayed on SAE–213–T22 and SAE–347H boiler steels by detonation
gun spray process. High temperature corrosion studies were conducted on the uncoated as well
as detonation gun sprayed specimens in a molten salt environment at 700uC under cyclic
conditions. The molten salt comprising Na2SO4–82%Fe2(SO4)3 was applied on the specimens as
a deposit. The weight change technique was used to establish kinetics of the corrosion. X-ray
diffraction, field emission scanning electron microscopy/energy dispersive spectroscopy and Xray mapping techniques were used to analyse the corrosion products. SAE–213–T22 steel
suffered an accelerated corrosion in the form of intense spalling of its oxide scale, whereas SAE–
347H steel exhibited only marginal spallation in the form of fine powder. The Cr3C2–NiCr coating
showed good adherence to the boiler steels during the exposure with no tendency for spallation
of its oxide scale. The coating was found to be successful in developing resistance against hot
corrosion in the molten salt environment, which may be attributed to the formation of oxides of
nickel and chromium.
