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Application of aluminum diffusion coatings to mitigate the KCl‐induced high‐temperature corrosion
Author(s) -
Kiamehr S.,
Lomholt T. N.,
Dahl K. V.,
Christiansen T. L.,
Somers M. A. J.
Publication year - 2017
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201609047
Subject(s) - materials science , scanning electron microscope , microstructure , metallurgy , corrosion , diffusion , chloride , energy dispersive x ray spectroscopy , aluminium , coating , high temperature corrosion , analytical chemistry (journal) , composite material , chemistry , physics , thermodynamics , chromatography
Pack cementation was used to produce Fe 1−x Al and Fe 2 Al 5 diffusion coatings on ferritic‐martensitic steel P91 and a Ni 2 Al 3 diffusion coating on pure nickel. The performance of diffusion coatings against high‐temperature corrosion induced by potassium chloride (KCl) was evaluated by exposing the samples at 600 °C for 168 h in static lab air under KCl deposit. In addition, a salt‐free experiment was performed for comparison. Microstructure, chemical and phase composition of the samples were analyzed with scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffractometry (XRD) before and after the exposures. It was found that all the diffusion coatings formed protective oxides under salt‐free exposure in air. Under the salt deposit, Fe 1−x Al showed local failure while on large parts of the sample a protective layer had formed. Fe 2 Al 5 was attacked over the entire surface and the dominant mode of attack was selective aluminum removal. Ni 2 Al 3 showed excellent performance and no sign of attack was observed anywhere on the sample.