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Cosmetic metal finishes and their benefits
Different types of metal finishes can offer unique benefits. While some finishes like metal plating and powder coating can increase durability and corrosion resistance, others, like painting and polishing, are more often used for aesthetic purposes. With so many different types of metal finishes, and because some are more common than others, it can be difficult to know which one is best for your project.
For the purposes of this article, we will focus on the four types of metal finishes mentioned above and examine the benefits of each type.
Types of metal finishes
Metal surfaces can be finished using a variety of methods. While some methods need additional material(s) to be added to the surface of a substrate metal, others necessitate the removal of material, and some don’t change the part’s dimensions at all. In much the same way that certain metals can’t fulfil all possible project requirements, certain finishes can’t be applied to all metals. So, it’s important to know the strength requirements and environmental factors that impact the part being produced. This determines the type of metal to be used, which in turn dictates the list of potential finishes.
1) Metal plating
Metal plating involves a chemical bath designed to add thin layers of other metals onto a part’s own metal substrate. The specific substrate determines what types of metal plating will work on the part. Common processes include zinc coating or anodizing. The chemical reactions and the addition of various metals (like zinc, chromium, or nickel) to the metal substrate give the part with additional properties it otherwise would not have. These extra layers of metal can improve the part’s durability and resistance to wear and tear. Additionally, the part’s resistance against chemical damage and corrosion improves. Finally, depending on the metals that are introduced, electrical conductivity may also be improved as a result of metal plating.
Improved chemical and electrical properties aren’t the only benefits of metal plating, though. The process can also enhance the overall appearance of a part. Though metal plating can be a complex and intensive chemical process, its cost can be justified for both small and large batches of parts.
2) Powder coating
Powder coating is a finishing process that involves the heat curing of a thermoplastic polymer powder onto a metal substrate and is generally compatible with aluminium, stainless steel, and carbon steel parts. Like painting, various colours and finishes can be achieved. The result is an aesthetically pleasing part with a glossy, semi-glossy, matte, metallic, or textured coloured surface. Powder coating is often more beneficial than simply painting a part because it gives greater protection against corrosion and normal wear and tear. The addition of thermoplastic material effectively shields the substrate material from making contact with the external environment. Additionally, for both small and large batch volumes, powder coating is more durable, robust, and economical than painting. Finally, powder coating materials generally do not contain solvents or volatile organic compounds (VOCs), making it a safe and preferred method of metal finishing.
3) Wet painting
Wet painting, though better for materials that cannot withstand high temperatures, can still achieve many of the benefits of metal plating and powder coating and is occasionally used prior to plating processes to add additional layers of protection. Before painting, substrate surfaces must be cleaned, dried, sanded, and primed with an appropriate primer. With wet painting, only a thin film is typically applied to the surface of the substrate. Additional undercoat layers can also be applied to give extra resistance to corrosion. Attractive cosmetic finishes can be achieved with wet painting and fillers can be used to hide joints and inserts within parts. Wet painting is easy to set up for small batches, but using it for larger batches may not be ideal.
Polishing, unlike the other metal finishes on this list, does not introduce any additional materials to the metal substrate. Instead, polishing produces a smooth and uniform natural finish by abrasive methods that reduce surface roughness after fabrication. This generally consists of sanding down the surface of the part and then polishing it with an appropriate polishing tool. This makes polishing an excellent option when trying to hide welded or riveted joints. But, because no materials are introduced, no corrosion protection is added by the polishing process. It is more suitable for metals that have inherent corrosion resistance like aluminium and stainless steel.
The application you wish to fulfil with metal parts determines the type of metal finish that can be used. While metal plating and powder coating are great options in terms of corrosion resistance and durability, they may not be ideal for small batches of parts all the time. Wet painting can offer many of the same benefits as metal plating and powder coating, but may not work so well for larger batches. Finally, polishing is a good option when trying to achieve a more natural finish, but it offers no additional corrosion resistance or durability.
Choosing the right metal finish for your project can be difficult when so many different types are available, but it doesn’t have to be. Contact a representative at Ludwick Precision today to discuss which cosmetic metal finish is best for your project.