Protect Aluminum Surface Finish?

Some ideas....

' For a new project... if you'll start with grade aluminum stock, it is naturally resistant to corrosion (even salt water) and 90% of your job will be complete before you even start. is one of the weaker grades of aluminum, but it is machinable and weldable. The bright, shiny traffic control cabinets you see at intersections are

un-treated, un-coated, un-painted

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sheet metal, and they look great year after year. If you want to attach this part to steel, brass, or concrete where galvanic corrosion might possibly start, then simply separate the 2 materials with a sheet of plastic.

' For a restoration project... there is an inexpensive (non-electroplated) dip process for aluminum. Technically it is a chromate conversion process. It has industrial names like Iridite, but you can do the same thing at home with a couple of buckets and a product called Alodine. (Do a Google search.) First you de-oxidize the surface by sanding and submerging in a strong base, then rinse, then submerge in the Alodine, then rinse again, then blow dry. Typically aluminum parts turn some shade of yellow, but the yellowing is solely indicative of the time spent in the Alodine and grade of aluminum. A 10-15 second soak will leave your part nearly silver. The amount of yellow color is an indicator of the level of corrosion resistance, so nearly clear would be very light protection, but it is still superior to almost every other coating for aluminum.

Furthermore, the chromate conversion leaves the perfect surface to accept paint, or in your case clear lacquer. Combining the 2 would give superior protection. However, you also need to understand that Anodizing (which you mentioned) is a time-consuming electroplating process that goes INTO the surface, and therefore has very good scratch resistance. Chromate conversion is a coating

on top of

the surface, and is not a good wear surface. But due to the simplicity and 100% coverage answers most of the needs of most parts.

Hope this helps.

The applications for aluminum alloys are varied, but for many projects, such as with infrastructure or medical products, the appearance of the final product counts. This means that having a variety of aluminum surface finishes creates more possibilities for what an aluminum extrusion can do. We will review what surface treatments provide and the different types of finishes available in the industry.

What advantages do aluminum surface treatments provide?  

Often just seen as a means of corrosion protection, these treatments can drastically impact a variety of conditions and properties. Such changes include:

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• Altering surface hardness and abrasion resistance
• Appearance
• Coating adhesion like paints, varnish, and bonding adhesives
• Providing protection from corrosion and durability

What types of aluminum surface finishes are there?

No matter the application, aluminum and its alloys provide the advantage of having a naturally hard and inert surface oxide layer. This layer is formed in aerated water and air and then re-forms when the metal is cut. Subsequently, the oxide film allows aluminum and its alloys to have minimal corrosion.

The surface finishes for aluminum fall into three main groups: anodizing, powder paint and liquid paint. Though not as common, there are other surface finishes which include mechanical finishes, pretreatment, and sublimation.

The Big Three: Anodizing, powder coating, and wet coating

• Anodizing ' Adding further protection beyond the natural oxide film, this electrochemical process provides durability to the aluminum. Anodized aluminum can accept vibrant colors and any aluminum alloy can be anodized. 

• Powder Paint' This process leaves behind a film that meets intense performance criteria. For example, there are many environmental regulations that prevent the use of VOCs which powder coating does not contain. It is applied as a solid, and when going through and over, the solid particles fuse to form the film.

Liquid Paint ' Varying in color, this film provides uniform thickness. Unlike powder coating, they do contain VOCs but they are driven off during the baking process. When these VOCs are removed, the volume solids form a film on the extrusion.