How to use weathering steel?

August 15, 2023

Weathering steel has excellent corrosion resistance. It has been widely used in buildings, vehicles, Bridges, towers and other steel structures. There are three main ways to use weathering steel: bare use, coating use and rust layer stabilization treatment.

1. Naked use:

The most common use of weathering steel is bare use. Generally, after 3 to 10 years, the rust layer on the surface of weathering steel gradually stabilizes, the corrosion development slows down, and the appearance is a beautiful chocolate color.

Because the process of stabilizing the rust layer of weathering steel is affected by the chemical composition of the steel, the use environment, the water retention and dust accumulation of the structural details and mechanical wear and other conditions, if the improper use destroys the formation conditions of the stable rust layer, weathering steel will also produce serious rust.

2, painting use:

In many departments such as buildings, Bridges, vehicles, etc., weathering steel and ordinary steel are mostly painted, and the weathering steel after painting shows excellent corrosion resistance compared with ordinary steel. However, due to the increase in the use of coating costs and operating procedures, it is difficult to widely use large components.

3. Use after stabilizing treatment

At the very beginning, a treatment is implemented on the surface of the component to shorten the formation process of the stable rust layer of weathering steel, which can avoid the phenomenon of yellow rust liquid hanging in the early use of weathering steel, prevent pollution, and at the same time form a stable rust layer. Although the bare use is an economic and unique use method of weathering steel, it takes a long time to complete the stabilization process of the rust layer in the natural environment. Before the formation of stable rust layer, the early rust liquid often polluted the surrounding environment by hanging and flying

Rust structure

In the process of using weathering steel, the initial stage is the same as ordinary steel, corrosion occurs, but then the corrosion rate gradually slows down, after a certain time, the corrosion is almost no longer carried out, so as to achieve the purpose of protecting the matrix, this phenomenon is called the stabilization of the rust layer, and the rust layer in this state is called the stabilization of the rust layer.

From the effect of corrosion products on the corrosion process, the atmospheric corrosion of steel is a process of electrochemical reaction of oxygen in the air through the rust layer in the presence of water film. The rust layer is composed of loose outer rust layer and dense inner rust layer, and the alloying elements in steel are mainly affected by the inner rust layer.

The rust layer is stabilized

Key point

(1) Rapid formation of stable rust layer: In the rust layer stabilization technology, how to effectively control early rust and form a dense and stable rust layer, so as to obtain FeOOH in the coating film is the primary key of the technology.

(2) The role of alloying elements: chromium and other metal elements replace goithite to form the final stable rust layer, which generally takes 10 years. How to select appropriate metal element ions to replace iron ions, speed up the replacement rate, and form a stable rust layer in a short time; Enrichment of cu, P, cr and other alloying elements in the rust layer is the second key of this technology.

(3) Organic coating materials: The research and development of rust layer stabilization treatment methods have three aspects: weather resistant film treatment, special oxidation coating treatment, iron oxide phosphate treatment. Whether as a coating material, or as a color carrier or binder, organic matter needs to have good weather resistance and corrosion resistance, the coating material should also have the characteristics of porous grid. It can not only allow a certain amount of air and water to supply the bottom layer until it forms a stable rust layer, but also prevent the initial rust liquid of weathering steel from hanging and flying, and maintain the appearance of beauty

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