Difference between electrogalvanizing and hot-dip galvanizing

Electrogalvanizing and hot-dip galvanizing are two common anti-corrosion treatment methods, which have significant differences in many aspects. The following is a detailed comparison of the two:
Principle
Electrogalvanizing: Using the principle of electrolysis, a uniform, dense and well-bonded metal or alloy deposition layer is formed on the surface of the workpiece through electrolysis. Specifically, the workpiece to be plated is used as the cathode, a specific metal material (such as zinc) is used as the anode, and an insoluble solid (such as lead plate) is used as a conductive medium. It is immersed in a solution containing ions of the metal material to be plated (such as zinc), and a direct current is passed. The anode metal dissolves to produce metal ions. Under the action of the electric field, the metal ions move to the cathode in a directional manner and deposit, thereby forming a coating.
Hot-dip galvanizing: also called hot-dip galvanizing and hot-dip galvanizing, is to immerse the rust-removed steel parts in a zinc solution melted at about 500°C, so that a zinc layer is attached to the surface of the steel component, thereby achieving the purpose of anti-corrosion. The principle is the process of forming an iron-zinc alloy between the iron matrix and the outermost pure zinc layer. The process can be divided into three steps, including the iron-based surface being dissolved by zinc liquid to form a zinc-iron alloy phase layer, the zinc ions in the alloy layer further diffusing into the matrix to form a zinc-iron intersoluble layer, and the role of aluminum elements.
Appearance
Electrogalvanizing: The appearance is relatively smooth and bright. The electroplating layer using the color passivation process is mainly yellow-green and colorful; the electroplating layer using the white passivation process is bluish-white or white, slightly colorful. The corners of complex workpieces are prone to “electric burning” and become gray, and the zinc layer in this area is thicker.
Hot-dip galvanizing: The appearance is relatively rough, the color is darker, and it is generally silvery white. Sometimes there will be water marks and a few drops on the surface, especially at one end of the workpiece.
Performance characteristics
Electrogalvanizing: The zinc coating is thin, with fine, uniform and non-porous crystals and good corrosion resistance; the zinc layer obtained by electroplating is relatively pure, corrodes slowly in acid, alkali and other mists, and can effectively protect the fastener matrix; the zinc coating forms a variety of colors after chromic acid passivation, which is beautiful and has a certain decorative effect; because zinc has good ductility, it can be cold punched, rolled, bent and other various shapes without damaging the coating.
Hot-dip galvanizing: A thick and dense pure zinc layer covers the steel surface, which can avoid the contact of the steel matrix with any corrosive solution and protect the steel matrix from corrosion; it shows unique corrosion resistance in general atmosphere, marine salt spray atmosphere and industrial atmosphere, and the zinc-iron alloy layer also has strong hardness, which can be used as a wear-resistant protective layer, and has good toughness and wear resistance; after hot-dip galvanizing of steel structural parts, it is equivalent to an annealing treatment, which can effectively improve the mechanical properties of the steel matrix, eliminate the stress during steel forming and welding, and is conducive to turning of steel structural parts.
Приложение
Electrogalvanizing: The fields involved are becoming more and more extensive, mainly used in machinery manufacturing, electronics, precision instruments, chemicals, transportation, aerospace and other fields.
Hot-dip galvanizing: With the development of industry and agriculture and the rapid development of transportation, construction, bridges, oceans, electricity, ships, petroleum, petrochemicals, agriculture and other fields, the application scope of hot-dip galvanized products is constantly expanding.
In summary, there are significant differences between electrogalvanizing and hot-dip galvanizing in terms of principle, appearance, performance characteristics and application scope. When choosing which galvanizing method to use, it is necessary to decide based on the specific application scenario and needs.