In 2013, the direct cost of 腐蚀 was 3.15人中的1%.1万亿美元.S. GDP, 哪一个 in June 2013 is estimated to equal $500.7 欧元. 腐蚀 is a an electrochemical process where the metal is oxidized by virtue of interaction with its environment, 哪一个 results in the metal returning to its most stable oxidative state. This article will discuss those factors that influence 腐蚀, especially in regard to the use of 涂料 designed to protect the metal to 哪一个 they’re applied. 相应的, consideration of the fundamental factors that influence 腐蚀 processes as it relates to the use of 有机涂层s will be considered herein.
Metals desire to be in their most thermodynamically stable state, 哪一个, in simplified terms, is the naturally occurring state of matter in its lowest energy state. Metals ordinarily exist naturally as oxides (e.g. 铁的氧化物, 氧化铝, 氧化锌 等.), because oxides represent their lowest energy state. Oxidation occurs at the anode (positive electrode) and reduction occurs at the cathode (negative electrode). 腐蚀 is normally accelerated by the presence of water, 氧气, and salts (particularly of strong acids).
Figure I lists a series of metals and their ability to resist 腐蚀. The most common metals used in industry include steel (cold rolled and hot rolled steel), 铝, galvanized steel (hot dip and electrogalvanized steel) as well as galvalume. The latter two metal substrates utilize either a 锌 layer or an 铝/锌 layer respectively on the surface of the steel to enhance 腐蚀 resistance.
Even though 铝 and 锌 are less noble than steel, when not coated with an 有机涂层, they provide longer-term improved 腐蚀 resistance than steel. When steel 生锈s, the 腐蚀 product (三氧化二铁) is loosely attached to the surface, whereas in the case of 铝 or a 锌/铝 alloy, the 腐蚀 products form a more tightly knit adherent layer to the metal surface that decreases the subsequent rate of 腐蚀 (Table III).
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