Oxidation by elecrolytic plasma - peo (version 1)
N.B.: The information contained in this sheet comes from reliable sources. Nevertheless, it is provided without any guarantee, express or implied, of its accuracy.
Principle:
Electrolytic oxidation by discharge causing the growth of a crystalline oxide film.
This process consists in imposing a potential difference between the part to be treated and a counter-electrode in a non-aggressive and non-polluting weakly concentrated alkaline medium and does not require an electrolyte with a dissolving action to obtain thick layers contrary to anodization. The nature of the electrolyte has an influence on the mechanical properties of the oxide and on the thickness of the film formed. The layers obtained are composed of two sub-layers: a very porous surface layer with poor mechanical properties and a more compact internal sub-layer with very good mechanical properties and very good adhesion to the substrate. This sub-layer represents 2/3 to 3/4 of the total thickness. The interface between the dense layer and the porous outer layer is located at the initial surface of the material. A very good surface finish can be obtained after removal of the porous surface layer and lapping.
The composition of the treated alloy and in particular its content of elements such as copper or magnesium have an influence on the thickness and hardness of the film formed.
ASPECT : depends on the finish
THICKNESS : a few tens of microns
MICRODURITY :1000 HV and more
SURFACE CONDITION : depends on the finish (see the aspect of the different undercoats)
ELECTRICAL INSULATION : yes depending on the thickness of the layer
COEF. OF CRACKING : good under medium load
SUBSTRATE:
All grades of aluminum alloys and for all processing methods. However the alloy influences the level of performance obtained and the appearance. This treatment can also be applied to Titanium and Magnesium alloys.
VARIANTS:
The name Electrolytic Plasma is sometimes replaced by Micro Arc Oxidation. Several commercial names exist
APPLICATIONS :
Resistance to corrosion, erosive or abrasive wear and good scratch resistance
Applications : dry pumps, automotive, aerospace ...
SELECTION CRITERIA - LIMITATIONS :
Size of the workpiece: the size of the workpiece depends on the high voltage electrical source and the electrical power delivered. It is possible to work with direct or alternating current. In order to obtain homogeneous thicknesses on parts with complex geometries, a counter-electrode whose shape follows the shape of the part to be treated is necessary. The current generator must allow a control of the current density, which is essential to obtain thick layers.
ENVIRONMENTAL IMPACT:
The process used has no critical influence on the environment, no heavy metals, no chlorinated solvents. There is therefore no threat to the sustainability of this process.
Implementation
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