Views: 147 Author: Site Editor Publish Time: 2026-03-07 Origin: Site
Brake discs are a crucial component of automotive safety systems. However, as exposed metal parts, brake discs have long faced severe corrosion challenges—whether in the humid environment of rainy days, the de-icing salt on roads in winter, or the high-salt fog of coastal areas, rust silently erodes the surface of the brake discs.
Corrosion not only affects the appearance of brake discs, but more seriously, it affects the precision and performance of parts, and can even cause significant economic losses and safety concerns. Even more challenging is the fact that brake discs generate heat through high-speed friction during operation, resulting in rapid temperature changes. This places far more stringent requirements on the temperature resistance and thermal shock resistance of anti-corrosion coatings than ordinary anti-corrosion coatings.
Traditional electroplating zinc or chrome plating processes, while providing some protection, carry the risk of hydrogen embrittlement—the treated material may experience hydrogen embrittlement fracture, a fatal flaw for brake discs subjected to enormous mechanical stress. Meanwhile, the widely used ordinary Dacromet coatings, containing chromium ions, have been gradually phased out by the automotive industry.
The corrosion protection of brake discs urgently requires a technological revolution.
Zinc-aluminum coating (Dacromet coating): A "protective armor" born out of this need
It is against this backdrop that zinc-aluminum coating technology emerged and quickly became the ideal choice for brake disc surface treatment.
As the name suggests, zinc-aluminum coating is a composite protective coating formed by using zinc powder and aluminum powder as the main fillers, combined with inorganic or organic binders. When applied to brake discs, it exhibits multiple protective mechanisms:
Firstly, cathodic protection through sacrificial anodes. Zinc has a more negative electrode potential than iron. When the coating forms an electrochemical circuit with the brake disc substrate, the zinc powder preferentially dissolves, thus protecting the iron substrate from corrosion.
Secondly, a shielding effect. Layers of flaky zinc and aluminum powder are stacked within the coating, forming a dense physical barrier that effectively blocks the penetration of water, oxygen, and corrosive ions. Studies have shown that optimal protective effects are achieved when the average size of the flake zinc and aluminum powders is controlled between 20-40 micrometers, and the zinc-aluminum mass ratio is between 3:1 and 7:1.
Thirdly, the stabilizing effect of the passivation film. By introducing rare earth ions (such as cerium and lanthanum) to replace traditional chromium ions for passivation treatment of zinc and aluminum powder, a stable passivation film can be formed in the coating, further enhancing corrosion resistance.
Technological Breakthrough: Overcoming the Dual Challenges of High Temperature and Corrosion
The biggest challenge in brake disc corrosion protection lies in high temperature. According to the automotive brake disc corrosion testing standard (GB/T 18684-2002), the coating corrosion resistance performance test requires pretreatment at 300℃ for 1 hour. At such high temperatures, many traditional coating binders decompose and condense, reducing their strength, toughness, and adhesion, producing pores and cracks, ultimately leading to a significant degradation in corrosion resistance.
How to solve this problem?
The key to the technological breakthrough lies in the innovation of binders. The latest patented technology demonstrates that by pre-treating organosilicon through hydrolysis, a film-forming component with high silicon content can be obtained, replacing traditional chromium oxides as a high-temperature resistant binder. This organic-inorganic composite component combines the high-temperature resistance of the inorganic component with the toughness of the organic component, resulting in superior overall performance.
Actual test data is encouraging: Zinc-aluminum coatings using this technology, with a dry film thickness of 20 micrometers after the first coating heat treatment, still exhibit a neutral salt spray resistance of over 900 hours after being treated at 300°C for 1 hour; if a second coating is added for pore sealing, the neutral salt spray resistance can be further improved to over 1000 hours.
In comparison, the salt spray resistance standard for automotive brake disc anti-corrosion coatings currently on the market, including some imported coatings, is typically only 150-240 hours. The technological advantages of zinc-aluminum coatings are obvious.
Shisheng Solution: End-to-End Supply Chain Guarantee from Coatings to Processes
As a leading company in the surface treatment field, Shisheng Group is at the forefront of the industry in the research and application of zinc-aluminum coating technology. In the coatings sector, Shisheng's independently developed MX7800 Dacromet coating liquid (zinc-aluminum coating) utilizes a high-tech formula and imported raw materials, exhibiting excellent adhesion, surface hardness, and salt spray resistance. This product can be directly coated onto the substrate without the need for an electroplating priming layer and is completely free of hydrogen embrittlement risk—crucial for components subjected to high stress, such as brake discs.
For scenarios with even higher protection requirements, Shisheng has also launched the MX3120 Dacromet topcoat (silver). This product uses nano-alloy powder, toughening agents, and film-forming agents as its main base materials, improving the coating's corrosion resistance, extending salt spray resistance to over 1200 hours, increasing surface hardness and leveling properties, and allowing for diverse surface colors.
In terms of processes, Shisheng has developed specialized coating equipment for brake discs. The SCX series of dedicated spray coating lines for automotive brake discs and exhaust pipes ensures uniform coating coverage on complex-shaped brake disc surfaces, eliminating blind spots. Whether it's dip-coating or spray coating, Shisheng can provide complete solutions from equipment to process parameters.
Application Verification: From Laboratory to Real-World Conditions
Excellent technical parameters are one thing, but verification through practical application is even more crucial.
In an application study at Anhui Jianghuai Automobile Co., Ltd., researchers applied zinc-aluminum coatings to the brake discs of a certain vehicle model, achieving ideal corrosion resistance requirements and providing important reference for the development and application of similar components in the future.
In the more severe tropical marine atmospheric environment, research institutions conducted outdoor exposure comparison tests on brake discs with different protective processes. The results showed that the optimized chromium-free zinc-aluminum coating exhibited excellent corrosion resistance and better environmental adaptability. This means that whether in the humid and rainy south, the snow-melting salt corrosion of the north, or the high-salt fog environment of the coast, the zinc-aluminum coating can provide reliable long-term protection for brake discs.
Green Future: Achieving Both Chromium-Free and High Performance
With increasingly stringent environmental regulations, chromium-free treatment has become an irreversible trend in the surface treatment industry. Responding to this trend, Shisheng Group launched the MX700 environmentally friendly Dacromet coating fluid specifically for brake discs, maintaining excellent anti-corrosion performance while eliminating chromium ions.
Further technological advancements have been made. By introducing rare earth ions (such as cerium nitrate and lanthanum nitrate) to passivate zinc and aluminum powders instead of chromium ions, and combining this with a high-silicon polymer obtained from organosilicon hydrolysis as a high-temperature resistant binder, the new generation of chromium-free zinc-aluminum coatings achieves a perfect balance between environmental protection and high performance.
From rust-covered to pristine, from chromium pollution to green environmental protection, zinc-aluminum coating technology is reshaping the protection standards for brake discs.
For the millions of cars on the road every day, this technology brings not only longer service life but also more reliable safety assurance. Shisheng Group will continue to deepen its research and application of zinc-aluminum coating technology, providing the global automotive industry with more perfect surface treatment solutions through leading technology, high-quality products, and comprehensive services.
