In order to preserve the coin, start with the deterioration of the character. The corrosion process of a coin depends on the chemical stability (composition) of the coin material, the material used in the packaging in contact with the coin, the atmospheric conditions in which the coin is stored, and the contact observation of the coin. In general, Kimbiban corrosion resistance, silver than copper corrosion resistance, zinc, aluminum, iron and other metals are more susceptible to corrosion. For alloys, sometimes it depends on the more chemically active metals, such as pure gold, which is more stable, and when copper is added to the gold to form an alloy, the coin is prone to black spots. But brass (copper and zinc alloys) is more corrosion-resistant in the atmosphere than pure copper. PVC in the packaging material is harmful to coins, PVC at room temperature will gradually precipitate plasticizers corrosive coins, which can cause irreparable damage, this point should be sufficient attention, especially for copper and copper alloy coins. Abroad, the dangers of using PVC have been widely recognized in the early 80, and the material has been phased out in the package of coins and converted to polyethylene. Substances such as water vapor, sulfide and carbon dioxide in the air are also harmful to coins, such as sulfur and silver reacting to silver sulfide, so that the surface of silver coins become gray and black. Moisture in the air also accelerates the oxidation process of coins.
During the appreciation process, contact the bare coin with your hands so that the sweat leaves fingerprints on the coin, and the dust in the saliva and air lands on the coin, which will speed up the corrosion process of the coin. In order to preserve good coins, first of all, we should choose the means of packaging, both easy to see, but also conducive to the protection of coins, depending on the conditions of the individual. Optional packaging has non-polyvinyl chloride plastic box, with polyester film round hole paper clips, polyester film bags, paper bags and so on. The optional materials are polyethylene, polypropylene, polyester film. In order to facilitate appreciation, can also be placed on the basis of transparent packaging in the collection coin book, the key point is not to choose PVC-containing materials to wrap the storage of coins, its harm must not be underestimated. In order to isolate air, there are generally two methods of gas tightness and vacuum encapsulation. Airtight refers to the isolation of air, but does not draw the air inside the package. The vacuum package will make the packaging material in close contact with the surface of the coin, which may also damage the coin. Packaging using thermoplastic pressure or ultrasonic fusion means, these means have not been widely used, generally only in the mint packaging of SGD and in the rating agency packaging after the grading of coins. The simplest way to isolate air is to soak the coin in anhydrous alcohol, a disadvantage that is not easy to see, but the effect is better. Coins should be stored in a clean, dry place with ventilation and air.