1. Standard Surface Treatment

Standard surface treatment primarily involves cleaning and deburring. Milling and tool marks may remain visible, with a maximum allowable surface roughness of Ra 125 microinches. This is the default finish for all CNC machined parts, requiring no additional processing, and is applicable to all machined materials.

The cleaning process aims to thoroughly eliminate surface contaminants such as oils, rust, dust, and cutting fluid residues. This not only enhances the adhesion and effectiveness of any subsequent treatments but also ensures parts meet hygiene standards and maintain stable performance during use. The deburring process specifically targets the removal of sharp edges and small protrusions generated during machining. These burrs can detract from aesthetic quality and potentially cause wear, scratches, or safety hazards. Through precise deburring techniques—including mechanical polishing, electrochemical deburring, or ultrasonic cleaning—parts achieve a smoother surface, improved overall machining accuracy, and extended service life. This foundation is essential for subsequent surface treatments like painting or electroplating.

2. Anodizing Treatment

Transparent Anodizing:
Transparent anodizing is an electrochemical process used to treat the surface of metals such as aluminum and its alloys. Its primary purpose is to form a transparent, dense oxide layer that enhances both corrosion resistance and aesthetic appeal.

• Definition and Principle:

• Definition: Transparent anodizing involves immersing metals (primarily aluminum and its alloys) in a suitable electrolyte and applying an external current to form a colorless, transparent oxide film on the surface. The coating thickness typically ranges from 0.0002 to 0.0012 inches. This treatment may cause a slight darkening of the part's original color.

• Principle: The process is based on electrochemistry. When a metal is immersed in an electrolyte, ions (e.g., oxygen, hydrogen) adsorb onto its surface. Under an applied current, these ions undergo electrochemical reactions, forming a protective oxide layer. The current's polarity is crucial in facilitating the growth of this oxide film.
  

  
  

3. Hard Anodizing (Type III)

Hard anodizing is an advanced surface treatment that produces an exceptionally thick and hard oxide coating on aluminum and its alloys, significantly exceeding the properties of standard anodizing. This coating greatly enhances the part's wear resistance, corrosion resistance, and scratch resistance, thereby substantially improving its durability and service life. Furthermore, the hard anodized surface serves as an excellent substrate for wet paint, coatings, or other secondary treatments, promoting strong adhesion between the coating and the base material.

It is important to note that while hard anodizing allows for some color variation, the considerable coating thickness (typically from 0.002 inches and greater) often results in darker or less vibrant colors compared to thinner coatings. However, this trade-off in color performance is compensated by superior physical protection and durability, making it highly valuable for demanding industrial applications.

4. Electropolishing

Electropolishing is an advanced surface finishing technology that utilizes electrochemical principles, combined with mechanical action, to precision-clean and polish steel parts. In this process, a specific current is applied between the part and an electrolyte, promoting the controlled dissolution of surface metal atoms. This effectively reduces surface roughness, removes micro-cracks, oxides, and other contaminants, thereby minimizing corrosion risk and significantly enhancing aesthetic quality.

Electropolishing not only imparts a uniform, smooth, and highly reflective mirror-like finish but also allows for precise control over the amount of material removed, typically between 0.0001 and 0.0025 inches. This precision ensures the final part maintains its original dimensional accuracy while achieving an ideal surface quality.

Additionally, the electropolishing process complies with internationally recognized standards such as ASTM B912, which specify electrolyte composition, processing conditions, and surface quality assessment, ensuring process consistency and reliability. Consequently, electropolishing is widely used in aerospace, medical devices, precision instruments, jewelry, and other industries where exceptional part surface quality is critical.

5. Heat Treatment

Heat treatment is a vital metalworking process that alters the internal microstructure of metal parts through controlled heating and cooling, significantly enhancing their material properties. This process can improve key characteristics such as hardness, toughness, wear resistance, and corrosion resistance, enabling parts to perform reliably in complex and demanding operating environments.

It should be noted that heat treatment can cause a color change in metal parts, often resulting in a shade darker than the original material. The specific appearance depends on parameters like the heat treatment type, heating temperature, soak time, and cooling rate. This color shift is typically a visual indicator of microstructural transformation and does not directly impact the part's functional performance.

Common heat treatment types include:

• Hardness Enhancement (e.g., Quenching): Processes like quenching increase hardness and strength through rapid cooling.

• Annealing: This process relieves internal stresses, reduces hardness, and increases toughness via slow cooling, improving machinability.

Heat treatment processes strictly adhere to international standards such as ASTM B917 or relevant industry specifications. These standards govern critical parameters including temperature ranges, time control, and cooling methods, ensuring consistent and reliable results. Compliance with these standards allows for precise control over the performance of metal parts, meeting specific application requirements.

6. Passivation Treatment

Passivation is a surface treatment technique specifically designed to enhance the corrosion resistance of stainless steel and other specific metal alloys. It is particularly suitable for 200, 300, and 400 series stainless steels, as well as precipitation-hardening and high-corrosion-resistant specialty steels. The process forms an extremely thin, dense passive film on the metal surface, effectively isolating the metal from direct contact with corrosive agents in the environment (e.g., oxygen, water, acids, alkalis), thereby significantly improving the material's corrosion resistance.

As a critical step in the metal processing sequence, passivation is often performed as the final cleaning and protective operation before packaging. This ensures that metal parts maintain their superior corrosion resistance during transportation, storage, and use, preventing premature corrosion caused by environmental exposure.

The passivation film is exceptionally thin, approximately 0.0000001 inches (nanometer scale). Despite its minimal thickness, its protective effect is substantial. This ultra-thin film does not alter the dimensional accuracy or mechanical properties of the part but significantly improves surface quality and corrosion resistance.

The passivation process strictly follows internationally recognized standards like ASTM A967, which provide detailed specifications for process parameters, film quality, corrosion resistance testing, and more, guaranteeing treatment consistency and reliability. Consequently, passivated metal parts deliver long-term, stable performance even in harsh environments and are widely used in chemical processing, petroleum, marine engineering, food processing, and other industries.