Rust Layer Stabilization Treatment

key point
(1) Rapid formation of stable rust layer: In 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 to this technology.
(2) The role of alloying elements: It usually takes 10 years for metal elements such as chromium to replace goethite to form a final stable rust layer. 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 period of time; enriching alloy elements such as cu, P, and cr in the rust layer is the second key to this technology.
(3) Organic coating materials: The research and development of rust layer stabilization treatment methods has three aspects: weather-resistant film treatment, special oxidation coating treatment, and iron oxide-phosphate treatment. Whether used as a coating material, a vehicle, or a binder, organic materials must not only have good weather resistance and corrosion resistance, but the coating material should also have the characteristics of a porous grid. It can not only allow a certain amount of air and water to be supplied to the bottom layer until it forms a stable rust layer, but also prevent the initial rust liquid from sagging and scattering in the weathering steel to maintain a beautiful appearance. [2]
R&D direction
(1) Stabilized rust layer + special coating, that is, weather-resistant film treatment (double-layer method).
When processing the weather-resistant film, first perform a weather-resistant base film treatment on the bottom layer to form an inorganic composite salt film with composite phosphate as the main component on the surface of the weather-resistant steel; then, apply acrylic paint on the composite salt film to form a breathable, Porous grid coating with good water permeability. The main function of the weather-resistant base film is to form a uniform, dense and stabilized rust layer on the surface of weather-resistant steel. The porous grid coating on the upper layer can allow a certain amount of air and water to be supplied to the bottom layer until it forms a stable rust layer. It can also prevent the rust liquid from sagging and scattering in the early stage of use, maintaining a beautiful appearance. After the stable rust layer is formed, this coating gradually disappears, and there is no obvious change in appearance at this time. However, the time it takes for the stabilized rust layer to change has a great relationship with the environment.
(2) Special oxidation coating treatment (single or double layer). During the oxidation coating treatment, the hydrophobic vehicle is mixed with oxide pigments and additives that promote rusting, and is coated on the surface of weathering steel to form an organic film. Due to the effect of this film, the rust liquid will not sag, and the organic film will disappear after a stable rust layer is formed on the surface of the weathering steel. In harsh environmental conditions, the impact of the environment is mitigated by adding a stable rust layer. The short-exposure oxidation coating begins to transition to a stable rust layer after a few months, and the transition time of the long-exposure oxidation coating takes about 1 to 2 years.
(3) Iron oxide-phosphate treatment (single or double layer). Iron oxide monophosphate is composed of primer and topcoat, and the treatment process is the same as that of oxidation coating. Primer contains phosphoric acid (phosphate) or iron oxide, etc., which can control early rust and form a dense and stable rust layer.