Surface Treatment: What is Dacromet? Differences from Galvanizing and Chromium Plating.

I. Basic Overview and Definition: Dacromet is a new type of anti-corrosive coating mainly composed of zinc powder, aluminum powder, chromic acid, and deionized water, also known as zinc-chrome coating. It was originally developed by American scientist Mike Martin to address the issue of chloride ions corroding the steel substrate. After being adopted by the U.S. military, this technology gradually gained global promotion and application, especially after being improved in Japan, it developed rapidly.

II. Main Components of Dacromet Coating Solution:

Metallic Powders: Zinc and aluminum powders are the main components of the coating, which protect the substrate in a corrosive environment.

Solvents: Typically inert organic solvents, such as ethylene glycol, are used to dissolve and disperse other components.

Passivators: Mainly chromic acid, chromates, dichromates, and their mixtures, which form a dense passivation film during the sintering process, enhancing the coating's corrosion resistance.

Special Organics: Such as cellulose white powder, used as a thickening and dispersing agent for the coating.

III. Anti-corrosion Mechanism:

The protective effect of Dacromet coating on the steel substrate is mainly reflected in the following aspects:

Barrier Effect: Flake-like layers of zinc and aluminum overlap, preventing water, oxygen, and other corrosive media from reaching the substrate.

Passivation Effect: Chromic acid reacts chemically with zinc, aluminum powder, and the substrate metal to form a dense passivation film.

Cathodic Protection: The zinc-aluminum-chrome coating provides cathodic protection to the substrate, similar to the function of a galvanized layer.

IV. Advantages:

Compared to traditional electroplating processes, Dacromet surface treatment technology has the following advantages:

Superb Corrosion Resistance: The rust prevention effect is 7-10 times better than traditional galvanizing, hot-dip galvanizing, or paint coating methods.

No Hydrogen Embrittlement: The process does not involve pickling and activation, avoiding hydrogen embrittlement.

High Heat Resistance: The heat resistance can reach over 300°C, much higher than traditional galvanizing processes.

Good Adhesion and Re-coating Performance: It has good adhesion to the metal substrate and is easy to spray and color.

Good Penetration: It can enter deep holes, narrow slits, and other parts of the workpiece to form a coating.

Pollution-free and Environmentally Friendly: There is no wastewater or exhaust gas emission during production and coating, meeting environmental protection requirements.

V. Disadvantages:

Despite its many advantages, Dacromet also has some shortcomings:

. Some Dacromet coatings contain chromium ions harmful to the environment and human health, especially hexavalent chromium ions, which are carcinogenic.

. The sintering temperature is high and the time is long, resulting in high energy consumption.

. The coating surface color is single, mainly silver-white and silver-gray, which is not suitable for personalized needs such as automobiles.

. The coating has poor electrical conductivity and is not suitable for parts used for electrical connections.

VI. Application Range:

Dacromet surface treatment technology is widely used in the following fields:

Automobiles and Motorcycles: Used for various high-strength chassis parts, engine surrounding metal components, etc.

Electrical and Electronics: Surface treatment of parts for high-grade home appliances, electronic products, etc.

Infrastructure: Anti-corrosion treatment of metal parts in subway tunnels, railways, bridges, elevated highways, etc.

Other Industrial Fields: Such as power, chemical, marine engineering, military industry, etc.

Dacromet differs significantly from galvanizing and chromium plating in many aspects. Here is a detailed comparison between the two:

I. Composition and Structure:

Dacromet: Dacromet (Dacromet) is a new type of anti-corrosive coating mainly composed of zinc powder, aluminum powder, chromic acid, and deionized water. It forms an inorganic protective layer on the metal surface through specific chemical reactions, which is composed of flake-like layers of zinc and aluminum overlapping and contains a passivation film formed by chromates.

Galvanizing and Chromium Plating: Galvanizing mainly involves coating the metal surface with a layer of zinc to form an anti-corrosive zinc layer. Chromium plating is about coating the metal surface with a layer of chromium, usually used to enhance the metal's aesthetics and hardness. In practical applications, galvanizing and chromium plating may refer to both processes being done simultaneously, but more often it refers to chromium plating after galvanizing.

II. Appearance and Aesthetics:

Dacromet: The metal surface after Dacromet treatment has a matte silver-gray appearance, which is very aesthetically pleasing and remains unchanged for a long time.

Galvanizing and Chromium Plating: The galvanized layer itself is usually silver-white, but after chromium plating, a bright chromium layer is formed, making the metal surface more aesthetically pleasing and harder.

III. Corrosion Resistance:

Dacromet: Dacromet coating has extremely high corrosion resistance and can keep the metal from corrosion in harsh environments for a long time. Its anti-corrosion performance is far superior to traditional galvanizing, even reaching 7-10 times that of galvanizing.

Galvanizing and Chromium Plating: The galvanized layer itself has certain corrosion resistance, but the corrosion resistance is enhanced after chromium plating. However, its corrosion resistance is generally not as good as Dacromet coating.

IV. Cost:

Dacromet: Due to the need for specific chemicals and equipment in the Dacromet process, and the high process requirements, its cost is usually higher.

Galvanizing and Chromium Plating: The cost of galvanizing and chromium plating is relatively low because the materials and processes used are relatively simple. However, it should be noted that if both galvanizing and chromium plating are done simultaneously, the cost will increase accordingly.

V. Environmental Friendliness:

Dacromet: The Dacromet process almost has no wastewater or exhaust gas emissions, meeting environmental protection requirements and is considered one of the representatives of green industry.

Galvanizing and Chromium Plating: Traditional galvanizing and chromium plating processes may produce certain wastewater, exhaust gas, and other pollutants, causing some impact on the environment. However, with the continuous development of environmental protection technology, modern galvanizing and chromium plating processes are also gradually transforming towards environmental protection.

VI. Application Range:

Dacromet: Due to its excellent anti-corrosion performance and environmental friendliness, Dacromet is widely used in automobiles, motorcycles, electrical and electronics, infrastructure (such as subway tunnels, railways, bridges, etc.), and other industrial fields with high anti-corrosion requirements.

Galvanizing and Chromium Plating: The application range of galvanizing and chromium plating is also very wide, but it is usually more focused on enhancing the aesthetics and hardness of the metal. For example, metal parts and decorative items with galvanizing and chromium plating are very common in the fields of construction, furniture, and decorative items.