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PEO of rheocast A356 Al alloy: energy efficiency and corrosion properties
Author(s) -
Mohedano Marta,
Matykina Endzhe,
Arrabal Raul,
Mingo Beatriz,
Zheludkevich Mikhail L.
Publication year - 2016
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.5815
Subject(s) - anodizing , materials science , microstructure , corrosion , alloy , mullite , dielectric spectroscopy , oxide , metallurgy , electrochemistry , coating , aluminium , amorphous solid , chemical engineering , anode , composite material , electrode , chemistry , crystallography , ceramic , engineering
PEO coatings were developed under voltage‐controlled mode on a rheocast A356 aluminum alloy without and with pretreatment by conventional anodizing in sulphuric acid. Microstructure and composition of uncoated and coated materials were studied using SEM, EDS and XRD. The anodic precursor oxide layer preserves the microstructure of the alloy because of the presence of secondary phases having a different behavior relative to the matrix during conventional anodizing. After PEO treatment, the coatings consisted of a mixture of α‐Al 2 O 3 , γ‐Al 2 O 3 , SiO 2 and mullite (3Al 2 O 3 ·2SiO 2 ). The effect of pre‐anodizing on energy efficiency was investigated revealing considerable energy savings with the precursor porous films, because of the faster establishment of the so‐called ‘soft sparking’ regime that promotes faster coating growth rate. The electrochemical corrosion properties were evaluated for uncoated and coated materials using electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy). PEO coated materials showed remarkably reduced susceptibility to corrosion. Copyright © 2015 John Wiley & Sons, Ltd.