Comparing Sheet Metal Finishes for Protection and Appearance

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Almost every sheet metal part that leaves our facility includes some form of finish. Whether it’s a special chemical coating to alter the surface of the metal, or one that changes the look of the part, sheet metal finishes are all around us.

Chemical Conversion Coatings

Conversion coatings have specialized purposes tailored to particular types of sheet metals. The most common types are: anodize, chromate, zinc, and passivate. Applying these helps limit corrosion that would normally happen when steel, stainless steel, or aluminum are exposed to the elements. But when you look at the chart below, you’ll notice that not all conversions work with all types of metals. For example, if you want to improve the electrical properties of stainless or aluminum parts, chromate is the way to go. However, if you want to improve corrosion resistance and add color to your aluminum parts, anodize them.

 

Material

Anodize

Chromate

Zinc

Passivate

Steel X X Corrosion Resistance X
Stainless Steel X Corrosion Resistance & Electrical Conductivity Corrosion Resistance Cleaning/Corrosion Resistance
Aluminum Corrosion/Wear Resistance & Decorative Corrosion Resistance & Electrical Conductivity X X

Two of the most common chemical treatment methods are galvanizing and galvannealing. These use zinc to protect steel from corrosion.

The Power of Powder Coating

One of the most common sheet metal finishes is powder coating. In this process, we take parts and run a small electrical current through them. Then, powdered polymer pigment is sprayed out of a nozzle toward your metal parts. The powder forms a bond with the metal through electrostatic attraction. After that, the powdered part is baked, creating a surface that hardens to become more rugged than paint. Another huge advantage powder coat has over paint is that the baking process dries powder faster than it takes paint to dry, and it gives a more uniform finish. We offer 30 different colors.

Finish Your Sheet Metal Part with Silk Screening

Silk screening as a sheet metal finish works exactly the way that it does on T-shirts. You’ve seen it everywhere. Often it’s used to add logos and iconic images such as USB port labels and explanatory text. In this process, we use a fine mesh screen that allows ink to transfer through it, but only in the areas where you want it to appear on your part. While it’s possible to layer different ink screens, it’s important to remember that drying time will add to your lead times and part cost.

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For more helpful sheet metal design tips, download our Design for Manufacturing (DFM) Guide.

 

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