Aluminium coatings anodic oxidation

Methacrylate polymers and copolymers employed to coat anodically oxidized and roughened aluminium sheets. The structures of the polymers are shown in Fig. 1... 

Anodic Oxidation Coatings on Aluminium, British Standard 1615 1972... 

Qualanod, Specifications for the Quality Sign for Anodic Oxidation Coatings on Wrought Aluminium for Architectural Purposes, Zurich (1983)... 

Hard Anodic Oxide Coatings on Aluminium for Engineering Purposes, British Standard 5599 1978... 

Method of specifying anodic oxidation coatings on aluminium and its alloys Specification for electroplated coatings of tin... 

This is a process in which the surface coating of oxide on aluminium (A1203) is made thicker. In this process the aluminium object is made the anode in a cell in which the electrolyte is dilute sulfuric acid. During the electrolysis process, oxygen is produced at the anode and combines with the aluminium. 

For coating the anodically oxidized and roughened aluminium sheets, dilute polymer solutions with 1% concentration in 2-butanone were applied without purification of the polymers synthesized as described above. The dry aluminium sheets were dipped in the polymer solution and kept there for 1 h. The coated samples were dried overnight and heated in an oven at 120° for 1 h. 

Relative atomic concentrations (at%) determined by XPS of anodically oxidized and roughened aluminium sheets coated with ferf-butyl methacrylate based polymer films and the degrees of coverage 0 calculated according to equation (1)... 

Conversion coatings offer many of the features identified as being desirable on a properly pre-treated metal surface consequently, they have been applied to a range of metals for the enhancement of structural adhesion. A number of studies have demonstrated that properly optimized conversion coatings are comparable to the anodic oxides in terms of providing durability with aluminium.Other studies have demonstrated variable adhesion performance with conversion coated aluminium adherends. A recent study has shown phosphated medium carbon steel to give better bond durability than grit-blasted and silane-treated material. ... 

British Standards Institute, BS 5599 (1993). Specification for Hard Anodic Oxidation Coatings on Aluminium and Its Alloys for Engineering Purposes. 

Sheet aluminium can be given a colour by a similar process. The aluminium is first made the anode in a bath of chromic acid (p. 377) when, instead of oxygen being evolved, the aluminium becomes coated with a very adherent film of aluminium oxide which is very adsorbent. If a dye is added to the bath the oxide film is coloured, this colour being incorporated in a film which also makes the remaining aluminium resistant to corrosion. This process is called anodising aluminium. 

In atmospheric exposure to industrial environments its corrosion rate is only about one-third that of zinc and the corrosion reaction is stifled by the tenacious oxide which is produced nevertheless it can frequently function as an anodic coating both for steel and for the less corrosion-resistant aluminium alloys. 

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