What are the surface treatment processes for Door Knob? What is the impact on service life?

In modern architecture and home design, Door Knob is not only a functional component, but also an important element that affects the aesthetics of space. Its surface treatment process directly determines the durability, corrosion resistance and user experience of the product.
1. Technical characteristics of mainstream surface treatment processes
Electroplating process
As the most widely used surface treatment technology, electroplating forms a metal coating on the surface of the substrate by electrolytic deposition. Among them, the chrome plating process (thickness 8-12μm) occupies the mainstream of the market with its mirror gloss and hardness (HV800-1000). Nickel plating (matte silver white) and copper plating (antique effect) provide more options for personalized needs. The difficulty of the process lies in the degree of pickling activation in the pre-treatment, which directly affects the bonding strength of the coating.
Anodizing
Mainly suitable for aluminum alloy materials, it generates a dense aluminum oxide film through electrolytic oxidation. The surface hardness of hard oxidation (film thickness 25-50μm) can reach above HV400, and the salt spray resistance test can reach 1000 hours after sealing treatment. The porous structure of the oxide film supports the dyeing process and can achieve rich color performance.
Powder spraying
The electrostatic spraying process is widely used on steel substrates. The epoxy-polyester mixed powder is cured at 200°C to form a 60-80μm coating. It has excellent impact resistance (50kg·cm) and weather resistance, but the surface hardness (HB grade) is relatively low, and it is easy to scratch after long-term use.
PVD vacuum coating
Physical vapor deposition technology can prepare decorative coatings such as titanium and rose gold. The film thickness is only 1-3μm but has extremely high hardness (HV2000+). This process is environmentally friendly and pollution-free, but the equipment investment cost is high, which is suitable for high-end product applications.
2. Correlation between key performance indicators and service life
Corrosion resistance
In the salt spray test, the time for white rust on chrome-plated parts is about 96 hours, the time for hard-oxidized parts is up to 720 hours, and the time for PVD-coated parts is more than 1000 hours. In actual use, chrome-plated handles in coastal areas corrode on average every 3 years, while the life of PVD products can be extended to more than 8 years.
Wear resistance
Simulation tests show that the thickness of the electroplated layer decreases by 15% after 5,000 frictions, the powder coating wears by 30%, and the PVD coating only loses 5%. In high-frequency use scenarios, the PVD process can maintain no obvious wear for more than 5 years.
Substrate bonding
In the cross-cut test, the adhesion of high-quality electroplated layers reaches 4B level (peeling area <5%), powder spraying is 3B level, and anodizing can reach 5B level. Insufficient bonding will cause the coating to peel off, exposing the substrate directly to the corrosive environment.
III. Technical and economic analysis of process selection
From the perspective of the full life cycle cost, the initial cost of ordinary chrome plating process is about ￥5-8 yuan/piece, and the average annual maintenance cost is 0.5 yuan; the initial cost of PVD process is ￥15-20 yuan, but the average annual maintenance cost is only 0.2 yuan. In places that focus on long-term benefits, such as high-end commercial spaces, the use of high-performance processing technology has significant economic advantages.