Let's first understand a few concepts and data before anti-corrosion of refrigerated containers. The metal corrosion process is generally carried out in two ways, one is chemical corrosion and the other is electrochemical corrosion. Chemical corrosion: Corrosion caused by direct chemical reaction between the metal surface and the surrounding medium. For example, metal corrosion caused by acid rain and acid fog. Electrochemical corrosion: Metal material (alloy or impure metal) is corroded by the reaction of the electrode when it comes into contact with the electrolyte solution. Such as the slow corrosion of iron products in a humid environment. According to statistics, the annual steel loss due to metal corrosion accounts for about 10% to 20% of the steel output that year. In other words, the corrosion rate of steel (on an annual basis) accounts for about 10% to 20% of the overall structure.
In view of the different processes of metal corrosion, the two common anti-corrosion methods are the isolation of chemically corrosive substances (such as acid rain and acid mist), and the electrochemical maintenance of target metals (such as the removal of highly metallic metals and maintenance The metal is placed close to each other, so that the metal with strong metallicity replaces the metal that needs maintenance to become the cathode of the galvanic battery, which is mainly oxidized to play the role of maintaining the target metal). Besides, electrochemical corrosion is the main proportion in the process of container corrosion. Since chemical corrosion is well prevented, the anti-rust topcoat can effectively isolate infection. However, small areas of paint film damage caused by scratches and other reasons are inevitable during the transportation of the container, and the corrosion process at the damaged part of the paint film is dominated by electrochemical corrosion, and after the formation of rust spots, the electrochemical corrosion process is dominated. It is a gradual acceleration process. At this moment, the maintenance of the topcoat on the damaged parts of the box is basically zero, so the prevention of electrochemical corrosion in the anti-corrosion process of the container becomes the top priority.
The container uses ship-specific paint (epoxy zinc-rich primer) for anticorrosion, which has an excellent protection against electrochemical corrosion of the container body. Since the paint contains a lot of zinc powder, evenly sprayed on the surface of the box will form a zinc maintenance layer. Since zinc is more metallic than iron, zinc will oxidize and rust before iron, so that iron can be effectively maintained (the principle of cathode maintenance in galvanic batteries). Even if the paint film is damaged, the zinc layer around the damaged area can still provide useful protection from infection to the damaged area, greatly reducing the process of iron corrosion. When using epoxy zinc-rich primer, it has a wide selection of topcoats, and can be used to a variety of outstanding anti-rust topcoats to enhance the isolation effect of chemical corrosive substances. Many large steel structure projects at home and abroad use epoxy zinc-rich primers, such as the main venue of the 2008 Olympic Games, the expansion of Beijing Airport, the expansion of Shanghai Pudong International Airport, and the Chongqing Chaotianmen Yangtze River Bridge. The main venue of the 2000 Sydney Olympics, the 2004 Athens Olympics, etc., all use epoxy zinc-rich primer.
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