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An environment‐friendly calcium phosphate conversion coating on AZ91D alloy and its corrosion resistance
Author(s) -
Sun R. X.,
Wang P. F.,
Zhao D. D.,
Sun Z. Z.,
Li C. Q.,
Chen K. Z.
Publication year - 2015
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.201307424
Subject(s) - coating , materials science , triethanolamine , corrosion , chromate conversion coating , conversion coating , scanning electron microscope , chemical engineering , alloy , metallurgy , substrate (aquarium) , phosphate , composite material , chemistry , analytical chemistry (journal) , organic chemistry , oceanography , engineering , geology
An environment‐friendly phosphate conversion coating free of chromate, fluorides, and nitrite was developed on AZ91D alloy through a facile chemical deposition method. The surface morphology and phase composition of the coating were characterized by field‐emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD). The corrosion resistance of the coating was evaluated by potentiodynamic polarization test in 3.5 wt% NaCl solution. Results indicate that the calcium phosphate coating was composed of a large number of leaf‐like and flower‐like particles. The chemical composition of the conversion coating was CaHPO 4 ·2H 2 O crystals. The coating can remarkably reduce the corrosion current density of the substrate. Introduction of triethanolamine (TEA) additive into the phosphating bath leads to denser coating and high anticorrosive property of the phosphate coating.