Does galvanized steel rust?
1. Galvanized steel sheet will rust. Depending on the environment where the galvanized steel sheet is located, the reaction will be different. If the galvanized steel sheet is left outdoors for a long time, the galvanized steel sheet will also rust. Du galvanized sheet is placed indoors and kept dry. Don’t let the galvanized sheet get water stains and corrosive liquid, so the rust time of the galvanized sheet will be prolonged.
2. It is a normal phenomenon that galvanized steel sheet is corroded and rusted because galvanized steel sheet contains other impurities, such as iron and zinc and other metals, which will easily produce corrosion effects and cause rusting of galvanized sheet.
3. Although the galvanized steel sheet has certain corrosion resistance and rust resistance, the capacity of the galvanized steel sheet is also limited. If it is placed in a harsh environment for a long time, all-steel sheets will rust.
Galvanized steel sheets are also divided into cold-dip galvanized steel sheets and hot-dip galvanized steel sheets. In general, cold-dip galvanized steel sheets are easier to rust, while hot-dip galvanized steel sheets are not easy to rust.
Why does galvanized steel rust?
During the entire service life of the galvanized sheet, the first corrosion that occurs is the oxidation of the galvanized layer on the surface to form “white rust”. After a little longer time, the “white rust” on the surface will further react with impurity gases such as carbon dioxide in the moist gas to form “black spots”.
When the galvanized sheet is used for a long time, the corrosion of the galvanized layer is severe, and the steel base loses the “sacrificial anti-corrosion” effect of zinc, and begins to oxidize to form “red rust”. When the steel base starts to oxidize and corrode, the speed becomes very fast, “the galvanized sheet also ends its life.
In addition, there are two special corrosion conditions of the galvanized sheet called “blackening”. One is that after the galvanized sheet is used for a period of time, due to the influence of elements such as lead in the galvanized layer, the matte part of the spangle will turn black. The blackened galvanized layer still has a protective effect on the steel base, but it has a certain impact on life. This situation has been greatly improved after the current suspension of lead and the use of antimony to promote the formation of spangles. Another situation is that the galvanized sheet is transported.
Due to the small coiling tension, the steel strip layers are loose, and the parts of the steel coil contacting the skid will rub against each other and cause oxidation. After the white oxide is rubbed off, the plating Black spots are produced on the surface of the zinc sheet, which will destroy the passivation film, thin the galvanized layer, greatly reduce the life of the galvanized sheet, and affect the appearance.
The galvanized sheet has excellent corrosion resistance in a dry environment and a pollution-free environment. However, in a contaminated environment, the life span will be greatly shortened, and it must be pre-coated into a colored board before use, which is what we often call a color-coated board.
Under normal circumstances, the corrosion of galvanized sheet is not that the galvanized layer on the surface is uniformly corroded, but the coating is corroded first where the coating and the substrate are poorly bonded, resulting in severe local corrosion and loss of performance. From this point of view, the adhesion of the galvanized layer, especially the overall adhesion, is more important than the thickness of the galvanized layer. If the galvanized layer has poor local adhesion, even if the galvanized layer is thicker, it will start to rust from the poor adhesion.
How to protect galvanized steel from rusting?
①Avoid quality problems such as insufficient passivation or insufficient thickness.
②Pay attention to the drying of water stains on the surface of the steel plate and keep it dry.
③Do a good job of smooth transportation and anti-scratch measures.
④Improve the storage conditions for storing steel plates, and the storage time should not be too long.
⑤The steel plate should be passivated with good passivation products.