How to Protect Against 腐蚀

腐蚀1

 

 

 

 

 

 

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 – 腐蚀 of Common Metals
Figure I – 腐蚀 of Common Metals

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  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).

Table III – 腐蚀 Loss of Uncoated Metals in microns/year in Various Environments. Exterior Durability of Organic Coatings, Eric V. Schmid, FMJ International, 1988
Table III – 腐蚀 Loss of Uncoated Metals in microns/year in Various Environments. Exterior Durability of Organic Coatings, Eric V. Schmid, FMJ International, 1988

 

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Identifying 屋顶 Failure Points

Chemical Dynamics has several decades of experience in the determination of the causes of 涂层 failures and the determination of probable cause of exterior 涂层 failures. Such 屋顶上的失败s may include 腐蚀, 油漆剥落, 颜色变化, 严重的粉化, cracking and spotting of 涂料 and damage due to 刮伤es.  Normally coated metal roofs will demonstrate accelerated failure rates versus 建筑 sidewalls, as exposure to the sun, wind and precipitation is more severe.

Failures may be caused by one or more of the following issues: poor cleaning and/or poor metal pre治疗, 质量差的金属, 油漆 degradation (pigment and/or resin) of either or both primer and topcoat, 油漆 formula defect, inadequate cure of 涂层, 油漆缺陷, 油漆 contamination, damage and 刮伤es during handling and 建筑 erection, and lastly aggressive climate conditions (chemical attack or environmental issues such as acid rain or a corrosive environment).

We have provided services including failure mode 分析, 建筑 site reports, 测试报告, 分析, expert witness reports, recommended failure remediation, and testimony on behalf of 建筑 owners as well as for companies that supply 建筑 materials.