Materials and Surface Treatments of Locks

1. Materials

When buying locks, people are generally worried that locks are not durable or the surface will rust or oxidize before long. That is related to what locks are made of and their surface treatments.

From the point of view of durability, the best material for locks is stainless steel, especially when used for their surfaces. The longer the material is used, the brighter the surface will be. Stainless steel has good strength, strong corrosion resistance and unchanged color. However, there are many kinds of stainless steel, which can be divided into ferrite stainless steel and austenite stainless steel. The former is magnetic. It will rust after long-term use or in an poor environment. Only austenitic stainless steel is anti-rust. Both of them can be identified with a magnet.

Copper is one of the most widely used materials for locks. It has good mechanical properties, good corrosion resistance and processability. Besides, it has bright color, especially the handles and other lock decorations forged by copper. Those have smooth surface, good density, no gas holes and no blisters. What's more, they are firm and rust-proof. And they can be plated with 24K gold or placer gold, which appears magnificent and noble.

The strength and anti-rust capability of the zinc alloy are not comparable to copper. But it has an advantage that it is easy to make parts with complex patterns, especially pressure casting. The locks with complicated patterns seen in the market are probably made from zinc alloy.

Steel, with better strength and lower cost, is easy to rust. It is generally used as the internal structural material of locks, and is not suitable for external decoration.

Ordinary aluminum alloy (except for aerospace) is soft and light, and its strength of materials is low, but it is easy to be processed and formed.

2. A surface treatment

A surface treatment generally refers to covering or forming a protective film on the surface of parts by metal electrodeposition (commonly known as electroplating), coating, chemical oxidation (coloring) or other processing methods. The film is anti-corrosive. At the same time, it also increases durability of products and improves their appearance, which are important factors to directly measure the quality of products. Common methods to measure surface treatments include coating thickness measurement, adhesion inspection, salt spray and moisture test, and appearance inspection, etc. As far as the coating is concerned, it is carried out through coating adhesion, hardness, moisture test and appearance inspection.

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