Below are common questions customers ask when selecting surface finishing options for investment cast and CNC machined metal parts.

A: Common surface finishing options include shot blasting, bead blasting, pickling, passivation, polishing, brushing, electroplating, electroless nickel plating, powder coating, black oxide, black nickel and PVD coating. The best option depends on the material, part geometry, corrosion requirement, appearance standard and working environment.

A: Yes. Stainless steel investment castings can be polished or brushed when a smoother and cleaner appearance is required. However, the final result depends on the casting surface condition, part geometry, required roughness and whether the surface will be visible in the final product.

A: For stainless steel castings, common options include passivation, bead blasting, polishing, brushing and electropolishing. If a black decorative finish is required, PVD coating can also be considered. The best choice depends on whether the priority is corrosion resistance, appearance, cleanliness or wear performance.

A: Yes. Stainless steel castings can be finished in black using options such as black PVD, black nickel or coating solutions. For stainless steel parts requiring a durable decorative black finish, black PVD is often a suitable option, but the final process should be confirmed based on the part material, tolerance and application.

A: In most cases, CNC machining is completed before the final surface finishing process. This helps protect critical machined dimensions, threads, sealing surfaces and mounting areas. However, some cleaning, blasting, pickling or pre-finishing steps may be done before machining depending on the casting condition and process plan.

A: Carbon steel cast parts usually require protective finishing because they are more prone to rust than stainless steel. Common options include black oxide, zinc plating, nickel plating, powder coating, painting or other protective coatings depending on the corrosion environment and appearance requirement.

A: Blasting is a mechanical cleaning process used to remove scale, oxide layers and surface residues while creating a uniform matte texture. Passivation is a chemical process mainly used for stainless steel to improve corrosion resistance by removing free iron and supporting the formation of a protective surface layer.

A: Yes. Powder coating can be used on many cast and machined metal parts, especially when a durable colored surface or outdoor protection is required. It is commonly considered for carbon steel, aluminum and hardware components, but the part surface must be properly cleaned and prepared before coating.

A: Yes. Some finishing processes add coating thickness or slightly change the surface condition. Plating, powder coating, PVD and other coating processes may affect tight-tolerance areas, threads, bores or sealing surfaces. These areas should be clearly marked on the drawing so they can be protected or controlled during finishing.

A: It is helpful to provide the part drawing, material grade, required finish type, surface roughness if applicable, color or appearance sample, corrosion resistance requirement, working environment and any critical surfaces that must be protected during finishing.