A comparative study of characterisation of plasma electrolytic oxidation coatings on carbon steel prepared from aluminate and silicate electrolytes

Abstract

Two kinds of PEO coatings were prepared on low carbon steel from aluminate electrolyte and silicate electrolyte, respectively. The coating surface and cross-section morphologies were observed by scanning electron microscope. The elemental and phase compositions were investigated by energy-dispersive spectrometer and X-ray diffraction, correspondingly. The scratch test was employed to examine the adhesion of the PEO coating. The electrochemical tests were used to evaluate the anti-corrosion property of PEO coatings. It was found that more substrate was oxidised during PEO process under the same constant voltage for the same length of time in silicate electrolyte than that in aluminate electrolyte. Besides, the silicate PEO coating grew faster than aluminate PEO coating. Compared with the uniform distribution of elements in aluminate PEO coating, silicate PEO coating exhibited a twolayered structure. The two-layered structure of the silicate PEO coating led to a negative effect on the adhesion. The aluminate PEO coating showed a better anti-corrosion property because of its denser structure.

Characterisation of Calcium- and Phosphorus-Enriched Porous Coatings on CP Titanium Grade 2 Fabricated by Plasma Electrolytic Oxidation

“…Nowadays, light metals such as titanium [1][2][3][4], niobium [5][6][7][8][9], tantalum [10][11][12][13][14][15], and their alloys [16][17][18][19][20][21][22], after electrochemical treatment (electropolishing and/or plasma electrolytic oxidation), may be used as biomaterials (implant materials) because of their mechanical properties [23][24][25][26][27], good corrosion resistance [28][29][30][31] in body fluids, and osteointegration [32][33][34]. The electropolishing…”

Growth of Anodic Layers on 304L Stainless Steel Using Fluoride Free Electrolytes and Their Electrochemical Behavior in Chloride Solution

“…On the other hand, Malinovschi et al [ 29 ] developed uneven, porous films in an electrolyte containing Na 2 SiO 3 and Na 2 CO 3 , formed mainly by amorphous SiO 2 , Fe 2 O 3 , and Fe 3 O 4 . However, Yang et al [ 30 ] compared aluminate and silicate electrolytes for growing anodic films in low carbon steel and evaluated their corrosion resistance. In this study, both anodic coatings showed a more positive corrosion potential and a lower corrosion current density than the substrate in 3.5% NaCl; but the layer developed in the aluminate condition (10 g/L NaAlO 2 and 1.5 g/L NaH 2 PO 4 ⦁2H 2 O) had a denser structure with better anti-corrosion properties.…”

Effect of Plasma Oxidation Treatment on Production of a SiOx/SiOxCyHz Bilayer to Protect Carbon Steel Against Corrosion

“…Amongst the most current reports found in the literature, the creation of protective barriers using plasma technologies stands out, be it the so-called hot plasma, or the one characterized as cold plasma, in which the substrates temperature remains close to the environmental 13 . In this context, some works use plasma electrolytic oxidation (PEO) techniques 1,2,14,15 and their variants 16,17 ; plasma transferred arc (PTA) 18 and thermal spray [19][20][21] , techniques in which the substrate usually reaches high temperatures. Other report deposition processes in low-pressure plasma 5,13,22 and in atmospheric-pressure plasma 22 .…”

“…Concerning the aforementioned techniques, most of them present as the main disadvantage the fact that the process develops at high temperatures 3,14,16,17 , limiting the treatment to heating resistant substrates. Also, the authors frequently report the presence of pores and cracks in PEO deposited coatings 1,3,14 , as well as adhesion problems and de-coating of the oxide layer formed on the treated metal 3 , characteristics that hinder the protection against corrosion.…”