Aluminium coatings electroplating

Aluminium coatings electroplated from ionic liquids are considered as an alternative candidate to replace cadmium ones. The present studies are aimed at obtaining dense aluminium coatings adherent to the substrate with a definite thickness and mechanical properties. 

The correlation between the parameters of electrolysis (current density, duration of electrolysis, temperature) and the morphology of the deposits on the stainless steel substrates was investigated. The analysis of composition, fine bulk and interface details of aluminium coatings electroplated from ionic liquids was performed by SEM, EDAX and FIB. 

Figure 5.1.3 (a-c) FIB analysis of fine bulk and interface details of aluminium coating electroplated from ionic... 

Figure 5.1.7 FIB analysis of aluminium coating electroplated from ionic liquid AI03 (—lOmA/cm )...

In the present studies, aluminium coatings were electroplated from commercially available ionic liquids (provided by BASF) based on EMImCl-aluminium chloride (AICI3) at a molar ratio of 40 60. 

Figure 5.1.2 SEM micrograph of aluminium coating on stainless steel electroplated from ionic liquid Al02...

Although the aluminium coating is dense and homogeneous at current density -20 mA/cm, the adhesion to the substrate is poor. At the current density -40 mA/cm, electroplating from ionic liquid A103 is not possible because of partial decomposition of the ionic liquid. 

Electroplated coatings (Section 12.1) Aluminium can be electroplated from molten salts or organic solvents. It can be plated on to other metals from fused aluminium chloride melts, e.g. 75[Pg.467]

Vacuum-deposited and electroplated coatings are pure metal with no chemical bond to the underlying surface. The properties will be those of pure aluminium. The presence of lacquer, in the case of vacuum-deposited coatings will, however, afford resistance to the passage of electricity and limit the maximum temperature of use. 

Resistance to abrasion The resistance to abrasion of electroless nickel-phosphorus hardened to 600 Hy, assessed by Taber abrasion tests, has been found to be double that of electroplated nickel However, electroless nickel coatings are not suitable for applications where two electroless nickel surfaces rub together without lubrication unless the values of hardness are made to differ by over 200 Hy units. Galling of aluminium, titanium or stainless steel may be overcome by applying electroless nickel to one of the two mating surfaces. 

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

Method for measurement of impedance of anodic coatings on aluminium Recommended practice for rating of electroplated panels subjected to atmospheric exposure... 

The technique may be said to combine the advantages of vacuum evaporation and sputtering, so that excellent qualities of adhesion are obtained without a limitation of maximum thickness of the coating—while at the same time the rate of deposition can be comparatively high. Many metals, alloys, and compounds may be deposited, on both metallic and non-metallic articles. However, its use at present is mainly for functional and protective applications, particularly where high resistance to corrosion is required. Thus, as examples, aluminium may be deposited on various types of steel and on titanium for uses in the aerospace and defence industries—and can be regarded as a less hazardous replacement for cadmium electroplating. 

Liu QX, El Abedin SZ, Endres F (2006) Electroplating of mild steel by aluminium in a first generation ionic liquid a green alternative to commercial Al-plating in organic solvents. Surf Coat Technol 201(3 ) 1352-1356. doi 10.1016/j.surfcoat.2006.01.065... 

Two types of specular references are used as standard materials. The first type, called first-surface mirrors, reflect incident radiation off the primary contact surface. These are typically vapor deposited or electroplated metals—gold, silver, rhodium, or aluminium on metallic or nonmetaUic (glass, quartz, or some other material that is thermally and mechanically stable) substrates. An important consideration is the flatness of the surface to be coated. The material must have minimal roughness and the surface must be as flat as possible to avoid measurement error. 

Caporah, S., Fossati, A., Lavacchi, A. et al. (2008) Aluminium electroplated from ionic hquids as protective coating against steel corrosion. Corros. Sci, 50(2), 534-539. 

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