Aluminium Conversion Coatings

 

Aluminium conversion coatings are non-decorative coatings applied to aluminium parts to achieve a thin electrically conductive coating that provides corrosion resistance. These aluminium conversion coatings can be used as a final finish and can also serve as a base for paints, high performance top coats, powder coats, lacquers or as a base for rubber bonding.

There are two types of aluminium conversion coatings:

 

Type 1 – Hexavalent Chrome

The components will range in colour from light yellow to dark yellow, depending on the immersion time in the chromate bath. The coating is soft and will not provide wear resistance. The chromate conversion coating provides an excellent base for painting and improves corrosion resistance when painted or unpainted. In general, the darker the colour the better the resistance.

  • Type 2 – Non-chromium Passivates

These passivates have been developed in response to the ELV, RoHS and WEE directives. Non- chromium passivates do not contain Lead, Cadmium, Chromium, Mercury or PBB/PBDE compounds. Initially, most non-chrome conversion coatings have been based on a combination of organic polymers and fluoride compounds. These processes give excellent paint adhesion characteristics but in most cases, have no corrosion properties.

Iridite NCP is the safe, reliable and cost effective alternative to chromate based pre-treatments for aluminium and has been developed in response to the ELV, RoHS and WEE directives. The Iridite NCP coating exhibits bare, unpainted corrosion resistance that is equal to hexavalent chromium on many aluminium alloys. This Iridite NCP coating requires simple application using spray, immersion or vertical flow.

In comparative corrosion tests on the most common aluminium alloys, Iridite NCP significantly outperforms chromate coatings, passing over 1000 hours neutral salt spray on all but the highest copper containing alloys. The electrical conductivity of Iridite NCP is comparable with conventional chromate coatings, so it is the perfect pre-treatment system for most electrical grounding applications. With its excellent paint adhesion characteristics, Iridite NCP is able to pass all standard paint industry corrosion and adhesion tests.

*Refer to the Iridite NCP brochure below for more detailed results and information.

 

PROCESS SEQUENCE:

1

Neutral degrease

2

Alkaline etch

3

Non-toxic acid etch

4

Nitric/Nitric free de-smutting

5

Chrome/Non-chromate conversion coating

            

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