Perfect your final products with one of these finishing methods for metal surfaces. Without them, the metal will appear scratched and incomplete. Finishing techniques offer different advantages, depending on the method you choose. Select the right method based on the attributes of the type of metal and number of pieces you’re finishing.
Chemicals and electricity create a metallic coating on the surface of individual pieces. This process, known as electroplating, places a layer of nickel, chrome, zinc or cadmium on the metal. Though this process does not smooth out errors in the metal’s surface, the coatings have advantages. Cadmium and zinc reduce rusting while chrome and nickel make the product more durable.
Unlike electroplating that cannot do anything about surface defects, some powder coatings can smooth these out. Powder coatings put a layer of durable melted plastic powder onto the metal. Finishes can be glossy, textured, or matte. Textured surfaces are best if surface defects exist. Glossy and matte finishes don’t do as good a job at hiding surface defects. This method is also not ideal if you have sharp edges that need to be smoothed out.
Like powder coating and electroplating, hot blackening coats the metal. This process uses a heated process to make the surface highly durable. The result has a black color, unlike other lighter-colored coatings. If color is more important than durability, don’t use hot blackening. Since it’s used to enhance abrasion resistance, hot blackening is best with harder metals. This coating is also ideal for heavy-use items, such as firearm components, hand tools, and auto parts.
Vibratory finishing is often used for large-scale projects. Though the equipment required is expensive, it operates faster than tumble finishing, according to Finishing Systems. If speed is of the essence for finishing numerous metal pieces, vibratory finishing is best. Though hand polishing works for individual pieces, you cannot get the same polishing effects from hand work as you can with a vibratory machine. This is an ideal method if you have surface defects you need to remove.
Grinding produces a wide range of finishes, but it requires skilled workers to use the grinders on individual pieces. This process takes time and multiple steps to achieve the smoothest finish. It’s best for mold-making where molds require precise, perfect smoothness inside. According to Mold Making Technology, good grinding requires three major steps – grinding, hand stoning and diamond polishing. With each step, the finish becomes smoother and finer.
Sand-blasting works best for large, flat surfaces that require a matte finish. This process requires special eye and respiratory protection for workers who use blasters that force tiny particles at the metal. Since it uses sand to shape the metal, this process is better for softer metals, which are more easily formed by the sand. As expected, skip sand-blasting for very small, fragile or highly detailed pieces.
Buff polishing does an excellent job with creating a smooth, non-textured surface. It uses a cloth on a polishing machine to give a rounded finish. While the finish can’t be topped with a buff polisher, it cannot be used if you have intricately designed metal pieces with small crevices the cloth cannot reach. It’s also not ideal for very fragile pieces.
Brushing metal gives it a uniform finish, thanks to the design of the machine. Unlike grinders, which require precise movements over the metal, brushing only needs the piece to be held against a belt. The brushing merges the best of buffing and grinding to smooth out defects and create a pristine surface. Special brushes may be used to create specific grains on the final product.
Choosing the Right Finishing Method
Not every job will require the same finishing method. Decide the technique based on the metal, its final use, and the cost. For mass production, consider tumble or vibratory finishing. Your available time and budget will narrow these options to one. Both methods have their own advantages.
Select from among the other techniques for smaller orders, but always consider the labor you have available. Never opt for grinding unless you have enough skilled laborers to do the job correctly. The finishing method you choose can define both your finished products and your bottom line. It’s not a decision to make lightly.