All About Metal Finishes

Intro

The finish of your part can completely change its function, aesthetics, and feasibility. There are even OSHA and federal requirements that might force you to use a certain finish. In other cases, a finish can help your part be more durable and reduce your downtime.

In this guide, we’re going to talk about metal finishes. All of the finishes we cover are offered at Rapid Axis — if you want to learn more or think your project can benefit from these finishes, reach out to us today.

Electroplating

Electroplating involves using some chemistry and electricity. A part is put into an electrolyte solution which means there are extra electrolytes that are looking for a home.

Electricity is then passed through the part, forcing metal atoms to adhere to the part, since the part has spare cations. 

You’re then left with a part that has an outer layer of whatever plating you just applied. If we did a zinc plating, then your aluminum part has a layer of zinc on the outside. The same is true for gold plating, which is what jewelers will use to make their products look nicer without spending extra money.

Electroless Plating

If you take the electricity out of electroplating, you essentially have electroless plating. In this style, a part is dunked in a solution of copper or nickel. As a result, the same catalytic process occurs as in electroplating.

Electroless plating results in a part that’s hard, low-friction, stronger, nonporous, and corrosion-resistant. It is also deposited as a “second skin” on top of the part, just like in electroplating.

Passivation

Passivation is a quick way to make a part corrosion-resistant. A metal part gets submerged in an acidic bath (usually citric or nitric acid), which gets rid of particles that are corrosive. Doing this will get rid of materials that can react with oxygen and rust in the future.

The cool part of passivation is that it can be done on stainless steel or aluminum alike — it’s not reserved for just non-ferrous metals.

Powder Coating

Powder coating is almost like paint on steroids. It’s applied to the outside layer of a part and comes in a powder form. The operator uses an electrostatic spray deposition (ESD) to apply the powder to your part. From there, the component will go into an oven where it’s heated and cured. During this process, a chemical reaction breaks down the powder and forces it to bind onto the part.

The benefit of powder coating is that you can specify the thickness, color, and any curatives used in the process. As a result, your part will look and act exactly as you’d like it to.

Powder coating adds protection to parts, making them more lubricious and corrosion-resistant.

Electropolishing

If you remember electroplating as we just described it, electropolishing is the opposite. In this process, a part’s outer layer of metal ions is removed from the part.

An electrolyte bath and electrical current are used to force the part into an anode, causing the metal ions to flow away from the part.

This comes in handy if you want to get rid of surface defects, rust, and small peaks and valleys along the surface of your part. It’s especially useful in stripping rust, and that’s the application that we tend to use electropolishing in.

Metal Grinding

Grinding is a rougher metal finish option. One of our machinists would use an abrasive machine that uses friction to smooth out the surface of your metal part. It could either be a handheld tool, bench grinder, wheel grinder, or a grindstone.

The concept works just like industrial-grade sandpaper. With sandpaper, an abrasive surface rubs against a part, removing peaks from the part through friction. The same thing is happening with our metal grinders, they’re just much more aggressive.

Abrasive Blasting 

Abrasive blasting is a general term that refers to blowing abrasive materials with high pressure. Common options are either glass beading or sandblasting. In these options, small coarse particles are blown with compressed air against your part.

The abrasives at high speeds will remove surface defects and smooth out your part.

It’s a much faster way of grinding and smoothing out a surface, which saves you time and money.

Conclusion

If you want to make your part stronger, longer-lasting, more colorful, and corrosion-resistant, you need to pick the right metal finish. If you want to get started with our experts at Rapid Axis, you can contact us today. Otherwise, reach out for a free quote and we’ll deliver high-quality, finished metal parts.

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