Steel drums are commonly used for the production of galvanized steel sheets. Since the steel sheets themselves have a galvanized layer, they are generally not required to be coated. In the production process, the seam welding of the galvanized steel sheet destroys the galvanized layer of the weld, thereby also destroying its corrosion resistance and aesthetics. Therefore, after the barrel is welded, the weld must be zinc-filled to restore its original function. Let us first talk about the difference between galvanized steel drums and galvanized steel drums.
The surface of the metal zinc tends to form a dense oxide film, so the zinc-plated steel sheet has more corrosion resistance than the ordinary steel sheet. The galvanized steel drum is formed by cold-rolling steel plate with the bottom cover and the barrel body, and then galvanized separately, and then packaged into steel drums. The zinc layer on the galvanized steel sheet is generally hot-plated, and the zinc layer obtained by hot-plating is thick, and its structural layer is composed of a steel substrate, a zinc-iron alloy layer, a zinc layer, an oxide film and an oil film, so The steel drum made of hot-dip galvanized steel has good corrosion resistance. Galvanized steel drums are steel drums made of such galvanized steel sheets.
The steel drum bottom cover and the barrel body are respectively formed and galvanized, and the electroplating zinc process is adopted. The zinc layer obtained by the process is that zinc ions are adsorbed by one action of the current, and the zinc layer formed is formed. The structure is loose and thin, and at the same time, due to the lack of heat penetration, the electrogalvanized sheet lacks a zinc-iron alloy layer, and the oxide film formed thereof is also thin and has no oil film layer protection. Therefore, the corrosion resistance and appearance of the electrogalvanized steel drum is not as good as that of the steel drum made of galvanized sheet. However, when the steel barrel body is made of galvanized steel sheet, the weld seam portion of the barrel may be etched or welded after being welded, so the galvanized layer here no longer exists. In order to keep the galvanized layer of the galvanized steel drum intact to ensure the overall corrosion resistance of the galvanized steel drum, the weld must be zinc-treated. At present, the zinc supplementation method adopted by the steel drum industry can be roughly divided into three types:
1. Hot-melt tinning method The hot-melt tinning method is to remove the oxide layer at the weld and then perform hot-melt tinning. The working principle is similar to the usual soldering (brazing), which is to clean the surface of the weld with a flux (usually a zinc chloride solution), then heat the weld, and finally apply the molten tin to the weld. You can sew it.
2. Aluminum paste recoating method The aluminum paste recoating method is to spray the galvanized steel drum special aluminum paste coating after grinding the oxide layer at the weld. The two-component coating is actually composed of an aluminum powder slurry dissolved in X-891 steel drum special coating (Shanghai Xugong Coating Technology Co., Ltd.), one component of which is a curing agent and the other component contains Anti-corrosion resin for aluminum paste.
3, spraying zinc method Spray zinc method is the best way to supplement zinc in galvanized steel drums, is to use zinc-plated steel barrel special weld zinc machine to carry out zinc and zinc. The special weld zinc filling machine for galvanized steel drum is mainly composed of two parts: sandblasting chamber and zinc spraying chamber.