Corrosion Protection of Aluminum

[Thane]

I am looking for a coating to protect aluminum (300 series casting and 6063-T5 extrusion) from corrosion by clorine bleach, ammonia, industrial cleaners, tap water, and bodily fluids. Some coatings I am aware of are hard coat anodize and powder coating.

Any recommendations or suggestions are greatly appreciated.

 

[JTreglio]

The military regularly uses ion-vapor deposited (IVD) aluminum to protect aluminum. Cadmium is another possibility, but cadmium is a carcinogen, so you don't want to work with it unless you absolutely have to.

Jim Treglio
Molecular Metallurgy, Inc.

 

[alexit]

You can also electroplate/vacuum deposition different materials (chrome, nickle, titanium, etc.) over aluminum depending on the costs you have in mind.

Alex

 

[rodriego]

Depending on the thickness, cost, and environment you may wish to look at Physical Vapor Deposition coated ceramics. A lower cost PVD alternative is aerosol sprayed coatings from such companies as

http://www.zypcoatings.com

and others. To research materials go to

http://www.matweb.com

Hope that this helps. Ken

 

[JTreglio]

PVD coatings can help reduce corrosion, but primarily by serving as a barrier. If the coating has pinholes, or is scratched, the substrate will corrode, often faster than if they were uncoated due to galvanic effects. Pure aluminum, cadmium, and zinc, on the other hand, act as sacrificial coatings. They are more reactive than the substrate, but their oxides are stable and cling nicely to the base metal. They protect even when the surface is scratched or there are holes in the coating. In fact, the standard military test for these coatings is to inscribe an X in panels down to the base metal, then put them into a salt spray chamber. When corrosion (red rust if the substrate is steel) is observed on the exposed surface, the coating is said to have failed. With a chromate conversion coating, IVD aluminum coatings run thousands of hours before failure. Without the chromate conversion coating, they still hold out for hundreds of hours.

Jim Treglio
Molecular Metallurgy, Inc.

 

[baldwinc4150]

There are also some inorganic coatings such as aluminum enamel that could be used for this application. Aluminum enamel is a fused glass coating.

 

[Thane]

Thank you for the suggestions.

Unfortunately our customers will sacrifice good corrosion protection for a lower cost product with less robust corrosion protection.

How does the cost and performance of PVD, IVD, and inorganic coatings compare to a Class 3 Hard Anodize and powder coating?

Has anyone had any experience with ecoat (electrodeposition of a polyurethane, epoxy, or acrylic)?

Thane