When it comes to metal finishing processes like anodizing and hardcoat, the design and fabrication of the parts themselves can significantly impact the final quality. An often overlooked consideration is the effect of sharp edges and corners on the finishing process. Whether dealing with welding or coating buildup, these seemingly minor details can significantly affect the durability and aesthetic appeal of the final product. 

Let’s explore why these elements matter and how to address them.

The Challenge of Sharp Edges and Corners

Whether on the part’s exterior or interior, sharp edges, and corners can create issues for anodizing and hardcoat finishes. Here’s why:

Uneven Coating Buildup 

The oxide layer that forms during anodizing grows perpendicular to the surface. Because there is minimal surface area on sharp edges and corners, the coating struggles to build up properly in those areas, which may compromise the protective properties of the finish.

Potential Corrosion Points

With less coating buildup, sharp corners can become vulnerable points for corrosion and wear over time, especially if the hardcoat is not sealed.

Thread Damage Risk

In the case of threaded holes, if the threads are machined too thinly, the anodic coating building can cause the threads to crumble when inserting a threaded component, posing a significant risk to the part’s functionality.

The Challenge of Welds

Welded aluminum parts can introduce another layer of complexity in metal finishing. There are a few critical reasons for this:

The Impact of Filler Material

The filler material used for the weld can affect the part’s final appearance after anodizing. The weld will have a different temper and composition than the rest of the piece, resulting in variations in shade and/or texture. 

The Risk of Pinholes

While not visible to the naked eye, thin spots or pinholes in the welded area can allow the chemicals used during anodizing to seep inside the part. This trapped chemistry can then leak out over time, causing cosmetic issues or potentially compromising the part’s structural integrity.

Weld Quality Matters

The overall quality of the weld itself is important when finishing. Well-executed, consistent, high-quality welds are less likely to have thin areas or pinholes that could create more significant problems.

Our Advice for Optimal Metal Finishing Results

There are some best practices to keep in mind during design and production planning that can prevent issues related to sharp corners, edges, and welds:

Add Radii and Avoid Sharp Edges

We recommend incorporating radii on edges and corners wherever possible to ensure uniform coating thickness and enhanced durability. This proactive measure minimizes potential corrosion points and improves the overall quality of the finish.

Take Additional Precautions with Welded Parts

When dealing with welded parts, ensure the welding quality meets the standard for all subsequent metal finishing services. Thin spots or pinholes in welds can lead to cosmetic and functional issues post-finishing. Considering a through-hole in welded parts facilitates better chemical drainage, preventing potential trapped chemistry from leaching out and negatively affecting the finish. 

Collaborate with Metal Finishing Experts 

Engaging with metal finishing experts early in the design phase is crucial. By simply reviewing resources such as our coating thickness cheat sheet and discussing specific requirements with our team, engineers can optimize designs for superior results. This collaboration ensures that potential challenges, such as the integrity of threads or the aesthetics of welds, are proactively and adequately addressed.

By addressing potential issues like welds and sharp edges from the start, you can help ensure an optimal metal finish that meets your appearance, durability, and performance requirements.

Contact our expert metal finishing team as early in the design process as possible – that way, we can mitigate risks and improve outcomes to produce optimal results on your final products.