Four Typical Surface Finishing Processes For Metal Parts

The performance of metal parts often depends not only on their material, but also on the surface treatment process. Surface treatment technology can improve properties such as wear resistance, corrosion resistance and appearance of metal, thereby significantly extending the service life of parts and expanding their application range.

This article will focus on four common surface treatment technologies for metal parts: electrolytic polishing, anodizing, electroless nickel plating, and stainless steel passivation. Each of these processes has its own characteristics and is widely used in automotive, aviation, electronics, medical equipment and other fields. Through the introduction of this article, you will have a deeper understanding of the principles, advantages and applicable materials of each surface treatment process.

Part One: Electrolytic polishing
Part Two: Anodizing
Part Three: Electroless Nickel Plating
Part Four: Stainless steel passivation

Part One: Electrolytic polishing

The processing of cavity parts is suitable for milling, grinding, turning and other processes. Among them, milling is a common processing technology that can be used to process parts of various shapes, including cavity parts. In order to ensure the machining accuracy, it needs to be clamped in one step on the three-axis CNC milling machine, and the tool is set by centering on four sides. Secondly, considering that such parts include complex structures such as curved surfaces, holes, and cavities, the structural features (such as holes) on the parts should be appropriately simplified to facilitate rough machining. In addition, the cavity is the main molded part of the mold, and its accuracy and surface quality requirements are high, so the choice of processing technology is crucial.

Electrolytic polishing

Part Two: Anodizing

Anodizing is mainly the anodizing of aluminum, which uses electrochemical principles to generate an Al2O3 (aluminum oxide) film on the surface of aluminum and aluminum alloys. This oxide film has special properties such as protection, decoration, insulation, and wear resistance.

Advantages: The oxide film has special properties such as protection, decoration, insulation, and wear resistance.
Typical applications: mobile phones, computers and other electronic products, mechanical parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration

Applicable materials: aluminum, aluminum alloy and other aluminum products

Part Three: Electroless Nickel Plating

Electroless nickel plating, also known as electroless nickel plating, is a process of depositing a nickel layer on the surface of a substrate through a chemical reduction reaction without external current.

Advantages: Advantages of this process include excellent corrosion resistance, wear resistance, good ductility and electrical properties, and high hardness especially after heat treatment. In addition, the electroless nickel plating layer has good weldability and can form a uniform and detailed thickness in deep holes, grooves, and corners and edges.

Applicable materials: Electroless nickel plating is suitable for nickel plating on almost all metal surfaces, including steel, stainless steel, aluminum, copper, etc.

lectroless Nickel Plating
Stainless steel passivation

Part Four: Stainless steel passivation

The process of passivating stainless steel involves reacting the stainless steel surface with a passivating agent to form a stable passivation film. This film can significantly reduce the corrosion rate of stainless steel and protect the base material from oxidation and corrosion leading to rust. Passivation treatment can be achieved by different methods, including chemical passivation and electrochemical passivation, the most common of which are treatments with strong oxidants or specific chemicals.

Advantages: The passivated surface of stainless steel has stronger resistance to pitting corrosion, intergranular corrosion and abrasion corrosion. In addition, passivation treatment is simple to operate, convenient to construct, and low in cost. It is especially suitable for large-area painting or soaking of small workpieces.

Applicable materials: various types of stainless steel materials, including but not limited to austenitic stainless steel, martensitic stainless steel, ferritic stainless steel, etc.


GPM’s Machining  Capabilities:
GPM has extensive experience in CNC machining of different kinds of precision parts. We have worked with customers in many industries, including semiconductor,  medical equipment, etc., and are committed to providing customers with high-quality, precise machining services. We adopt a strict quality management system to ensure that every part meets customer expectations and standards.


Post time: Mar-02-2024