Peyman Taheri, Mahmood Aliofkhazraei, Changiz Dehghanian and Alireza Sabour Rouhaghdam
Plasma electrolytic saturation (PES) treatments were applied on the surface of AISI H13 steel and corrosion resistance of the treated samples was investigated using…
Abstract
Purpose
Plasma electrolytic saturation (PES) treatments were applied on the surface of AISI H13 steel and corrosion resistance of the treated samples was investigated using electrochemical test methods. The aim was to obtain optimal corrosion resistance of the differently treated samples.
Design/methodology/approach
Nitrocarburized and boride layers were produced on AISI H13 steel by the means of the PES technique. Different experimental parameters during each treatment provided different microstructural and electrochemical properties. The techniques used in the present investigation included X‐ray diffraction, SEM, potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS).
Findings
The plasma electrolytic nitrocarburising coating was characterized by lower integrity than a PEB coating. All PES coated steels had a noble electrochemical behavior compared to the untreated steel. Different nano‐structures and morphologies obtained by different experimental parameters produced different electrochemical behaviors.
Practical implications
The results obtained in this research into PES techniques can be used wherever good corrosion resistance with the highest efficiency is required.
Originality/value
The speed of treatment by plasma electrolytic saturation techniques makes this method very suitable for industrial production of components.
Details
Keywords
Vahid Afshari and Changiz Dehghanian
The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their…
Abstract
Purpose
The purpose of this paper is to demonstrate the effect of grain‐size reduction on the stability of passive films formed on pure iron. Possible mechanisms capable of their improvement are discussed.
Design/methodology/approach
Nanocrystalline iron was produced by pulse electrodeposition using a citric acid bath. The grain size of the nanocrystalline surface was analyzed by X‐ray diffractometry and atomic force microscopy. The tests were carried out in 95‐97 percent H2SO4 aqueous solution. The stability of the passive films was investigated using Tafel polarization curves and electrochemical impedance spectroscopy measurements.
Findings
The corrosion resistance of Fe in concentrated sulfuric acid solution increased as the grain size decreased from microcrystalline to nanocrystalline. The decreased passive current density of nanocrystalline Fe may be due to the more rapid formation of continuous passive films at surface crystalline defects, compared with coarse‐grained Fe structures.
Originality/value
The behavior of passive film growth and corrosion is considered in terms of excess free energy caused by the nanocrystalline surface.