Surface Finishes
The choice of the right surface finish is one of the most important facets for obtaining the perfect product parts. There is a wide range of choices (glossy, matt, textured), the suitability of which also depends on your material of choice. In this overview you will find all kinds of frequently used surface finishes.
Types of Surface Finishes
Polishing: Polishing products is done to give them a high gloss. This can be done as a pre-treatment and as a final treatment. All metals can be polished, but the treatment is most often applied to: copper, brass, silver and aluminium. Before polishing, the product usually has to be ground to remove the deepest scratches.
Enamelling: Enamelling is the application of a glass-like coating to materials, the most important of which are: sheet steel, aluminium, cast iron, stainless steel, copper and glass. This gives a number of significant benefits such as, highly corrosion resistant, good adhesion, easy to clean.
Galvanising: By immersing steel in molten zinc at 450 °C, the hot-dip galvanising process creates a protective coating on the steel surface consisting of an alloy of iron and zinc surrounded by a highly adhesive layer of pure zinc. Zinc serves as a sacrificial anode that protects the steel against corrosion until the zinc-iron alloy layer has lost its effect completely.
Plating: In the plating process the surface of the metal is covered with a different kind of metal. This provides some useful benefits such as changing conductibility, inhibiting corrosion, heat resistance, boosted solderability and hardening the metal. Plating can change the performance and quality of the metal.
Anodising: The anodic layers formed are generally colourless, glassy, hard, wear-resistant and corrosion-resistant. Immediately after the anodising process, the layer formed has a porous structure. During the colouring process these pores are coated with a paint solution, after which a seal treatment is applied to close the formed layer. The thickness of the layer after anodising varies between 5 and 20 microns. The anodised layer can be applied dimensionally stable.
Plastic dip-coating: For products that have a complex structure, an immersion coating can be applied to improve the surface roughness. Plastic immersion coating is often used to coat metal products such as electrical wiring and wire hangers. In addition to preventing rust by protecting the metal from exposure to the open air, plastic coating also prevents the metal from contaminating anything it comes in contact with. This is especially useful with wire hangers, as the coating can prevent clothing from becoming stained.
Tumble finishing: In metalworking, this is also called barrelling. The parts are put into a horizontal barrel that rotates. The spinning gives the parts a smooth finish.
Sandblasting: This is the process of treating the surface of a component by blasting it with an abrasive under high pressure. The type of media used again determines the quality of the resulting finish. Sandblasting or blasting with a combination of air and water can quickly cover a large area. It can also improve some of the mechanical properties of metal by increasing its fatigue strength and improving its corrosion resistance through shot blasting.
Wetblasting: Wet blasting is a unique alternative in the sense that the granules are sprayed onto the pollution together with water. The strategy remains the same: the top layer and the pollution are scraped away by grains with a specifically chosen roughness. However, the addition of water provides some advantages. Under the pressure of the water, the remaining surface will feel more even. Furthermore, no fine dust will end up in the air, but the particles of dust will be caught by the water and end up on the ground.
Other types of Surface Finishes
Calendering: Calendering is the forming of a thermoplastic mass between two or more rollers into a film. Calendering is an industrial technique. A plastic thermoplastic is heated and kneaded into a viscous form and then processed between two or more rollers into a cooled foil or band of a certain thickness. Calender rolls are used for the production of plastic film and rubber products. Even the smallest defects in the roll surface, such as pores or cracks, are excluded to ensure the best product quality. The more precisely the calender rolls are ground, the lower the product tolerance values.
Burnishing: Transparent plastics such as plexiglass and polycarbonate can be marred by scratches. Polishing can make the plate clear again. How you proceed with this depends entirely on the severity of the damage. Polishing can be done by hand or by machine, with fine or coarse means. If you are going to saw plastics, you also need to polish the edges to achieve a clear cut.
Honing: Honing is a finishing process used to improve the geometry of a part, readjust the alignment of features such as bores and holes, and produce a finer surface finish. In the honing process, a small, abrasive, bonded stone is rotated over the surface of a part over a controlled path. The honing stones are built with an abrasive grain held together with adhesive. Honing is a high-precision process and is used to improve certain form characteristics such as cylindricity, surface finish, or sphericity.
Powder coating: A powder coating is a coating that is applied as a powder and which flows out into a closed layer by heating. Nowadays, there are various binders for powder coatings such as polyesters, acrylates, polyurethanes and epoxy-polyesters. In addition to the binder, a powder coating contains pigments, hardeners, additives and fillers. Powder coating is extremely broad and versatile in its application and is used, among other things, for (balcony) fences, machine parts, windows and window frames, furniture, decoration and design articles, bicycle and motorbike frames.
Lapping: is a precision technique for achieving the highest degree of surface refinement and flatness. It involves a skilled craftsman using a soft iron tool in combination with a mild abrasive slurry to slowly work the surface by hand with random, light and non-linear movements. This fills microscopic voids in the surface and flattens high spots.
Superfinishing: Superfinishing is used to refine the surface finish of a component to produce a very fine surface with an exceptionally low roughness average (RA). A fine-grit abrasive stone or tape is rotated over the component while the component is simultaneously spun in the opposite direction. Superfinishing will increase the life of a part by decreasing tear and weather. It can also be performed to achieve a tighter tolerance and better sealing capabilities.
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