Stainless Steel Laser Coloring: An Innovative Ink-Free Color Marking Technology

In fields such as metal processing, decorative design, and product traceability, color marking is an important means to convey information and enhance aesthetics. Traditional metal coloring methods like printing and electrochemical treatment have drawbacks such as environmental pollution, the need for additional consumables, and unstable colors. Stainless steel laser coloring technology, however, has emerged as a popular trend in the laser industry due to its advantages of no consumables, high precision, and long-lasting colors. By inducing an oxidation reaction on the stainless steel surface with laser energy to form a colored oxide film, it requires no ink or chemical reagents. It not only achieves rich colors but also ensures the wear resistance and environmental friendliness of the marking, providing new possibilities for the personalized processing of stainless steel products.

 

The core principle of stainless steel laser coloring is to use laser energy to induce the formation of an oxide film of a specific thickness on the metal surface. Then, through the inherent color of the oxide film and light interference effects, a variety of colors are presented. The MOPA fiber laser commonly used in experiments emits laser light with a wavelength of 1064 nm. When irradiated on materials such as 304 stainless steel, it raises the temperature of the irradiated area, triggering an oxidation reaction with oxygen in the air to form a dual-phase oxide film composed of chromium and iron oxides.

 

The thickness and surface morphology of the oxide film directly determine the final color—oxide films of different thicknesses have different reflection and refraction effects on visible light, thus presenting various colors such as blue, purple, pink, and yellow. For example, a thinner oxide film may appear purple, and as the thickness increases, the color gradually transitions to pink and yellow. More interestingly, laser coloring does not require complex equipment. Through galvanometer scanning and F-theta lens focusing, the formation of the oxide film can be precisely controlled on the stainless steel surface, enabling flexible applications from local marking to large-area coloring.

The core challenge of stainless steel laser coloring is achieving accurate reproduction of target colors through parameter adjustment. The key parameters affecting color include laser power, scanning speed, and repetition frequency. These three parameters do not act independently but determine the coloring effect through a fixed proportional relationship. Research has found that as long as these three parameters maintain the same proportional coefficient (laser action proportional coefficient), even if the specific values are different, extremely similar colors and oxide films can be generated on the stainless steel surface.

 

For example, a laser power of 20W, scanning speed of 100mm/s, and repetition frequency of 200kHz will produce the same color as a power of 30W, scanning speed of 150mm/s, and repetition frequency of 300kHz due to the consistent proportion. At the same time, parameters such as pulse width and focal length also affect the quality of the oxide film: when the pulse width is fixed at 4ns and the focal length at 210mm, the spot diameter can be stabilized at 50μm, making coloring more uniform. This parameter proportionality rule solves the problem of difficult color reproduction in traditional coloring and provides reliable parameter guidance for mass production.

 

Compared with traditional coloring processes, stainless steel laser coloring has distinct advantages. Firstly, it is environmentally friendly. The entire process requires no chemical reagents or ink, only utilizing the oxidation reaction between laser and air, producing no wastewater or waste residue, and complying with environmental protection requirements. Secondly, the colors are stable and long-lasting. The formed oxide film is closely combined with the stainless steel substrate, featuring strong wear resistance and resistance to fading, and can adapt to complex working conditions such as outdoor and high temperatures. Thirdly, it is precise and flexible. The laser spot is small and highly controllable, enabling both fine text and pattern marking and large-area uniform coloring, adapting to stainless steel products of different specifications.

 

In addition, laser coloring has the characteristics of a simple process flow and no consumable loss, which can reduce production costs. For example, in product traceability, laser coloring can be used to mark color QR codes on stainless steel parts, which are not only clear and easy to identify but also less likely to wear than printed marks. In the decorative field, it can achieve gradient colors and complex patterns on stainless steel plates, enhancing the aesthetic value of products. These advantages have made it popular in industries such as hardware products, medical devices, and architectural decoration.

 

The application scenarios of stainless steel laser coloring technology are constantly expanding. In industrial production, it can be used for brand logos and specification parameter marking of stainless steel products, where color marking is both eye-catching and anti-counterfeiting. In the decorative design field, it can endow stainless steel doors, windows, furniture, and artworks with personalized colors, breaking away from the monotonous texture of traditional stainless steel. In the high-end manufacturing field, such as medical devices and aerospace components, color marking can be used for part classification and traceability, improving production management efficiency.