Zinc-Aluminum-Magnesium Coated Steel Plates – the Frontier of Anti-corrosion in Steels

1. What is Zinc-Aluminum-Magnesium Coated Steel?

Zinc-aluminum-magnesium coated steel, also known as ZAM coated steel, is an innovative steel finish with superior corrosion resistance. Initially, pure zinc alloys were mostly used to enhance the corrosion resistance of metal surfaces. With the continuous innovation of steelmaking technology, corrosion-resistant coated steels such as zinc-aluminum alloys and ZAM alloys continue to emerge on the market, which greatly enhances the corrosion resistance of steel surfaces. 

2. Composition and Classification of Zinc-Aluminum-Magnesium Coated Steels

Zinc-aluminum-magnesium coated steel refers to a coated steel in which a certain amount of Al, Mg is added to the existing hot-dip galvanized coating or a certain amount of Mg is added to the hot-dip galvanized coating. It has high performance of corrosion resistance and high trimming protection.

A generalized analysis of magnesium-containing coated steel for commercial applications shows that the Mg content in most coatings is less than or equal to 3%. Hence, according to the aluminum content of the coatings, the zinc-aluminum-magnesium coatings can be divided into the following types:

• l Low-aluminum Zn-Al-Mg coating, with aluminum content of 1-3.5%: This coating is formed by adding a certain amount of aluminum-magnesium and other elements on the basis of hot-dip galvanizing. The coated steel plate has also been tested in a color coating unit, and low-aluminum zinc-aluminum-magnesium plate has also been successfully developed. The coating is an upgraded version of the corrosion resistance of the hot-dip pure zinc coating, which is referred as BZM coated steel plate and its color coated plate.

• l Medium-aluminum Zn-Al-Mg coating, with aluminum content of 5~11%.

• l High-aluminum Zn-Al-Mg coating, with aluminum content of 55%. The coating is formed by adding certain magnesium and other elements on the basis of hot-dip aluminum-zinc. The coated steel plate has also been tested in a color coating unit, and the color coated steel plate with a high-aluminum zinc-aluminum-magnesium substrate has been successfully developed. This coating is an upgraded version of the corrosion resistance of the hot-dip aluminum-zinc coating, which is referred to as BAM coated steel sheet and its color coated sheet.

3. Comparison between Galvanized (GI), Aluzinc, and Zn-Al-Mg Coated Steels?

Pure zinc coating is a kind of economical anti-corrosion coating, with a zinc content of not less than 99%. It can be further divided into galvanized steel with or without spangles, and these two types have almost the same level of corrosion resistance. However, if the steel plates need to be sprayed or painted later, those without spangles will have a more pleasant aesthetic. The thick zinc layer products usually have spangles (for example, the weight of the zinc layer is 275g/m² on both sides).

Aluminum-zinc coating is an alloy metal, in which the aluminum content is 55%, and the zinc content is 43.5%, with remaining component being silicon. Generally, the corrosion resistance of aluminum-zinc coating is 2-6 times better than pure zinc coating of the same weight. The surface of the galvanized steel coil can be modified by production technology to produce beautiful and uniform spangles, which can be directly used for exterior building or household appliances.

But there are also some disadvantages of aluminum-zinc coating:

First, the welding performance of the aluminum-zinc coating is not as good as that of pure zinc, so the welding process should be minimized in use;

Second, the protection of the aluminum-zinc coating on the cut of the steel plate is less than that of the pure zinc coating, and far less than that of the zinc-aluminum-magnesium coating.

The zinc-aluminum-magnesium coating has an excellent all-rounder performance. Its manufacturing cost is only slightly higher than Aluzinc coating, while its corrosion resistance is much better. In addition, it also has good performance to protect the cut of the steel plate, and the welding performance is equivalent to galvanized steels.

Currently, application cases of the Zn-Al-Mg steel plates are emerging in the market. At the same time, Zn-Al-Mg color-coated steel plate are also being mass-produced and widely used.

In the future, as the requirements for materials in construction and various industries gradually increase, zinc-aluminum-magnesium coated steel sheets may gradually replace the aluminum-zinc steel sheets in the market.

At CUMIC, we are constantly adapting our products and services to your processes for maximum efficiencies in your best interest. If you'd like to know more about Zn-Al-Mg coated steels, don't hesitate to leave a message below or reach us via marketing@cumic.com!

About CUMIC

CUMIC Steel has more than 15 years of experience in global steel trading, providing both steel mills and end-users with professional, efficient, and reliable steel supply solutions. We have established long-term cooperative relations with more than 200 steel mills to ensure these products are fabricated using quality material and are in line with various international standards.

We are a team of professional, passionate, and committed steel experts who dedicate our continuing efforts to the best experience of all steel users and everyone in the supply chain. We offer technical support, 3^rd party quality control services, steel marketing intelligence information, and many other value-added services to you. Get in touch today via cumic@cumic.com, and keep updated by following us on LinkedIn and Facebook.