What are Anodizing Grab Marks?

Anodizing Grab Marks

Anodizing serves as a great way to elevate the appearance of your aluminum trim or extrusion. Customize your project with anodized colors and add an extra layer of protection against damaging environmental elements that can affect the appearance and surface of the aluminum. The action of anodizing aluminum is an electrochemical process that involves submerging the aluminum extrusion or trim into a sulfuric acid bath that transforms and brings consistency to the appearance of the extrusion surface. The aluminum material must be held firmly in place by attaching to the extrusion on each end by bolting or clipping directly onto the aluminum in order for the aluminum to be dipped into the tank. This racking or fixturing process is what creates grab marks in anodized aluminum extrusions.

Aluminum Racking Marks

The aluminum grab marks also referred to as aluminum racking marks, are the result in the anodizing process from grabbing directly onto the aluminum that allows the electrical current to flow through the aluminum trim. This electrical current allows the oxygen ions that are released from the electrolyte in the anodizing tank to combine with the aluminum atoms on the surface layer of the aluminum trim which then creates the desired custom anodized finish.

The size and placement of aluminum racking marks vary with the size and shape of the aluminum trim to be anodized as well as the racking method used to attach to the aluminum extrusion. This variance in grab mark appearance and location is based on the amount of electrical current that must pass through each piece of aluminum extrusion and it will change with the size and shape of the aluminum extrusion that is to be anodized. Generally, the anodizing grab marks are found on one or each end of the aluminum trim within one to three inches from the end and are about the size of a pencil eraser. The contact points of the aluminum grab marks remain in mill finish (non-anodized) from the extrusion process.

What if you don’t want anodized grab marks visible on your project?

When the aluminum trim is racked or fixtured before anodizing, the material is secured on one or each end as electrical contact points (leaving behind racking marks). The pieces of anodized aluminum extrusions will typically have the grab marks within one to three inches on one or each end of the extrusion. This standard location of racking allows you the option to remove the grab marks from each end and results in minimal waste. When cutting off the anodized grab marks your piece will have the raw or exposed mill finish ends where the material was cut.

In cases where you would prefer the ends of your aluminum anodized, the racking marks can be strategically placed on the aluminum in locations that may not be visible once your project is completed. There are many variables that will determine the size and visibility of the racking marks. When anodizing aluminum, part size, weight, and shape all play an important role in determining the exact location of and what method will be used to secure onto the aluminum extrusion resulting in various grab marks.

Excellent Customer Service

Eagle Mouldings is proud to offer a wide variety of anodized aluminum extrusions and trims available for next day shipping as well as a large selection of custom colors and finishing options to help customize your project with the exact anodized finish you’re looking for. Check out our custom anodizing colors and contact our knowledgeable customer service team members for more information about our stocked or custom aluminum anodizing.


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