Surface grinding rmetal parts requires skill, and it’s time-consuming too because it involves multiple steps to give individual pieces an optimal finish.

Know the Different Ways to Finish Metal Surfaces

May 15, 2019
Various techniques may be considered. Understanding these eight options will help to make an informed decision and achieve the perfect surface

Metal products need proper finishing treatments, which can be achieved by applying a thin, complementary layer to a part’s surface. In fact, various metal finishing processes can be employed, according to the different applications intended for particular parts. The goal is to perfect the metal surface so the finished product looks flawless.

Each finishing techniques brings its own set of advantages. Depending on the method selected, you may look forward to the following benefits:
•  Better electric conductivity
•  Improved electric resistance
•  Enhanced chemical resistance
•  Improved tarnishing resistance
•  Better potential for vulcanization
•  Enhanced sturdiness
•  Augmented visual appearance

Some considerations may help you pick the most suitable metal finishing technique, including:
•  The speed of the technique in applying the finish to the part.
•  The cost of the finishing machine.
•  The hardness of the metal (harder metals require more intensive techniques and tougher abrasives.) 

Based on the material you’re working with, you may choose among the following metal finishing techniques:
Electroplating — Electroplating involves creating a metallic coating on the surface of individual parts using chemicals and electricity. A layer of chrome, nickel, and cadmium or zinc is placed on the metal surface.

Electroplating provides numerous advantages, including improved product durability, resistance to corrosion and surface friction, and enhanced visual appeal.

While electroplating metal does not smooth surface defects, the coating is still beneficial. Cadmium/zinc will reduce rusting, while the chrome and nickel will add strength to the product, making it more robust.  

Grinding — Grinding has the potential to create an array of finishes. However, this technique requires a bit of skill as the process is time-consuming due to the several steps involved that give individual pieces the smoothest finish.

Grinding machines harness friction and either attrition or compression to smoothen a metal surface. Grinding is considered as the best method for making molds which require perfect smoothness.

Of course, different types of machines can be used to achieve varying levels of smoothness. A ball grinding mill, for example, will work well to grind cement products, but may not be suitable for more extensive smoothing jobs.

Sand blasting — Sand-blasting, also known as bead blasting, is the most suitable finishing technique for large, flat surfaces that need a uniform, matte texture. The process requires workers to use specialized eye and nose protection gea,r as their work involves using blasters that force sand and tiny steel shots as well as metal pellets or other abrasives into a substrate at high speed.

This process is better for finishing softer metals as it uses sand to shape the metal, and results in a smooth, clean surface texture. However, avoid sand blasting when working with very small, fragile or intricate pieces.

Powder coating — Powder coating works well for smoothing surface defects as it creates an attractive finish, akin to paint, but with higher durability. It works by adding a layer of durable melted plastic powder over the metal surface to produce a textured and matte/glossy coating, as desired.

A textured, powder coating machine also does a good job of removing surface defects. However, avoid this method if your surface has sharp edges that need smoothing.

Hot blackening— Hot blackening involves spreading a thin layer of black oxide over a metal surface to produce a black-colored matte finish that’s highly durable and abrasion-resistant. For this reason the technique works best with harder metals.

This method entails a high-temperature process in which the product is inserted into several different tanks containing cleansers, caustics, and coolants.

Often, this coating process is used in the finishing of heavy items, including automotive parts, firearms, and hand tools. 

Vibratory finishing — Vibratory finishing is often used to deburr surfaces and remove sharp edges. The material is placed into a drum filled with abrasive pellets and a substrate. This step is followed by applying tumbling vibration to produce a uniform texture.

If you want to finish a number of metal pieces quickly, this is an effective technique. While individual pieces can be polished by hand, using vibratory finishing will produce a much better result. It is considered ideal for removing surface defects.

Metal brushing — Brushed metal finishing gives a surface a uniform finish and removes surface defects. This technique helps produce a uniform, parallel grain texture to even out the product’s surface.

Metal brushing calls for a piece to be held against an abrasive belt: the brushing is done to smooth defects and create a clean surface. Specialized brushes may be used to create precise grains on the finished part. The singular direction of the belt and brush leads to slightly rounded edges, perpendicular to the grain. 

Buff polishing — If you want to create a smooth and untextured surface, buff polishing will do the job. This technique employs a cloth wheel to buff the product’s surface and impart a rounded and glossy finish, with perfect luster. Because of the wheel’s limited range, the technique is less effective for pieces that have delicate and detailed features, or those with tiny crevices. It is commonly used for ornate products that require a certain degree of sheen and smoothness.

Metal finishing is a job that requires patience and a good understanding of product application and the various finishing options available. The speed of the technique plays a role in selecting a suitable finishing method, as does the hardness of the metal substrate.

Furthermore, cost is a critical factor.

The various metal finishing techniques mentioned here will help you arrive at an informed decision when treating a particular surface.
Vernon Glick is a marketing executive in the manufacturing sector.

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