Which Welding Finish Does Your Part Need? (Updated for 2024)

Last updated on January 4th, 2024 at 08:45 am

At Approved Sheet Metal, we take pride in our robust mastery of all things sheet metal fabrication—from materials sciences to the nuances of hardware selection to finishing options. As with sheet metal finishes, we’ve developed a proprietary system for classifying welding finishes to make selections easier for our customers.

Our team has 20+ years of experience welding prototypes to low-volume production quantities. We provide in-house welding capabilities, including MIG, TIG, and spot welding.

Understanding the 3 Classes of Welding Finishes

Our best-in-class welders can achieve any of the three classes of welding finishes to meet our customers' needs:

1. Class A Welds

The most expensive option, a Class A weld provides the best, most refined finish possible. Class A welds showcase a beautiful grain and are exceptionally smooth; these welds can look like some plastics, appearing completely seamless.

Class A welds are often reserved for cosmetic finishes and higher-priced projects as they require more time and effort to achieve. First, one of our welders lays down the beading. Then we give the weld a few quick passes with a Scotch-Brite wheel to maximize smoothness and minimize decolorization. Finally, we use a stroke sander or polisher and regrain the metal.

2. Class B Welds

A step down from Class A, Class B welds are less refined but not completely untreated. The surface isn't as smooth as a Class A weld but is flatter than a Class C weld.

Class B welds are often requested for internal parts or parts that will undergo further finishing treatments. Powder coating, for instance, will cover most imperfections associated with Class B welds.

To achieve a Class B weld, one of our welders lays down the beading and then uses the same Scotch-Brite wheel treatment as they would for a Class A weld. A couple of quick passes of the Scotch-Brite wheel reduce decolorization, and the Class B weld is complete. There is no final grinding or polishing step—the Class B weld is slightly raised but mostly smooth.

3. Class C Welds

The sheet metal fabrication shop standard, especially for internal parts, Class C welds are "raw" or untreated.

These welds aren’t ground down, polished, or smoothed. Instead, they are left raised in their original welding state with a visible edge.

All custom sheet metal welding projects begin as Class C welds. Class C welds can then become Class B welds and ultimately level up to Class A welds.

Welding Finish Consideration: Material Selection

The most common materials we weld are aluminum, stainless steel, and steel. When you look closely at examples of these materials with Class A, B, and C welds, you can see how the welds appear different on each material.

Aluminum

Aluminum is a strong candidate for each of the three classes of welding finish.

Many customers opt for aluminum when welding is involved because it can be polished and grained as a Class A weld, smoothed out a bit as a Class B weld, or left raised in its original Class C weld state.

Aluminum can be anodized and finished to look smooth, but welding finishes on stainless steel typically look even nicer.

Stainless steel

Any welding finish is achievable with stainless steel, but the Class A weld is particularly impressive. It's an excellent choice for external parts or any parts that require cosmetic finishes.

Looking at the Class C welding finishes for stainless steel versus aluminum, you can see how the natural weld is much darker on the stainless steel due to the material’s properties.

When selecting a welding finish, it's essential to keep coloration in mind. Upgrading a Class C finish to a Class B finish on a stainless steel part can significantly reduce discoloration, should that be necessary.

Steel

We'll cut to the chase—we do not offer a Class A weld finish for steel, as most parts will be powder coated or finished with orbital sanding. Steel is minimally corrosion-resistant, so steel parts typically receive finishing treatments that protect the metal and cover the weld, rendering a Class A welding finish unnecessary.

A Class B weld is the most common for steel parts and is better than a natural weld state for parts that will undergo finishing treatments.

How to Know Which Welding Finish Is Best for Your Part

Still not sure which welding finish is best for your custom sheet metal fabrication? Ask yourself these three questions:

• Is the part internal only? A Class C weld might be acceptable.
• Are you working with a tight budget or timeline? A Class B or even Class C weld is likely sufficient, provided you don’t need a refined, superior finish.
• Will there be other finishing treatments such as anodizing, powder-coating, or orbital sanding? Depending on your finishing treatments, you may not need to spend the time and money on a Class A weld.

When in doubt, the Approved Sheet Metal team is here to help you. We're happy to discuss your project and recommend a welding finish that suits your specifications and budget.

Are you ready to get started on your next custom sheet metal welding project? Let's work together! Request a quote today.