Alodine / Chromate Conversion

Gold Hexavalent Chromate Conversion Coating

At Electromold we perform an immersion process creating a Chemical Conversion coating on aluminium. These coatings are designed to provide improved corrosion resistance and a superior surface for better adhesion of primers and paints on bare aluminium. The treatment converts the aluminium surface with a superficial layer containing a mixture of chromium compounds, producing an aluminium oxide and chromic oxide layer.  At Electromold we call this coating Alodine or as it more commonly known "Chromate Conversion".

Electromold offers Hexavalent chromium that is goldish in colour and complies to the military specification MIL-C/DTL-5541 Type 1 Class 1A or Class 3.

All chromate conversion coatings use chromic acid in the form of its soluble salts. During the process, a thin film is produced on the aluminium surface. Chromate is an excellent treatment method for paint or adhesives since it greatly enhances the products ability to form a bond with the aluminium. It is frequently used on electrical and electronic equipment, the benefits are coating that provides increased corrosion resistance while remaining electrically conductive.

The oxide files produced by this process vary in colour from iridescent golden tan, depending on the aluminium alloy being treated, surface conditions, and the class of chromate requested.

There are generally two types classes available, Class 3 coatings are a lighter film and provide an excellent preparation for paint applications while still providing great electrical conductivity. Class 1A coatings are a heavier coating and are used for increased corrosion protection.

Both Class 1A and 3 coatings performed by Electromold conform to the following Military Specifications and pass a 5% neutral salt spray test at 168 Hours. The two most common specifications are MIL-C-5541 Class 1A or 3 and MIL-DTL-5541, Type 1 Class 1A or 3

Properties

  • Increased Corrosion Resistance (no sign of corrosion after 168 hours at 5% neutral salt spray test IAW ASTM B117)
  • Class 1A coatings are intended for use to provide corrosion protection
  • Improves paint adhesion for a range of finishes
  • Class 3 coatings are intended for use where lower electrical contact resistance is required, as tested passes 168 hours 5% neutral salt spray test IAW ASTM B117
  • Hexavalent chromium used
  • Works on alloyed and cast aluminium
  • Inexpensive

If you require any further information regarding this process or any of Electromold’s plating processes, please contact us on (03) 9464 0922 and one of our technical staff will be able to assist you.