A+-+corrosion+in+bridges

__**What is corrosion?**__
 * Topic: How do engineers slow down corrosion in bridges?**

- Formation of an oxide of iron due to oxidation of the iron atoms in solid solution is a well-known example of electrochemical corrosion, commonly knows as rusting. - It produces oxide(s) and/or salt(s) of the original metal -In other words, corrosion is the wearing away of metals due to a chemical reaction. - Corrosion can also form compounds such as oxides, hydroxides and sulphides, depends on the condition. EX: 4Fe + 3O2 + 2H2O - > 4FeO + 4OH EX: 4Al + 3O2 - > 2Al2O3

__**Method to slow down the corrosion**__ //Note: Corrosion involves the oxidation of the metal.//
 * +Anodic protection**: Anodic protection,by making a metal stucture anode, in which a low voltage direct current imposed between the exposed parts of a structure and the ground, so that it attains and retains an electrochemically passive state in a particualr environment (usually in an extremely corrosive environments, such as the handling and storage of concentrated sulfuric acid). It discourages oxdiation and favours reduction. Therefore, it tends to cause protection.

+ Passivation is the spontaneous formation of a hard non-reactive suface film that inhibits further corrosion. This layer is usually an oxide or nitride that is a few nanometers thick.
 * +Passive cathodic protection (a.k.a. sacrificial protection):** Passive cathodic protection, in which an anode made of a more reactive metal (such as magnesium alloy) is sacrificed to protect a structure acting as cathode. It is more widely applied as an anti-corrosion control technique in electrolytically conducting environment(ex: seawater).


 * +Chemical inhibitors:** It works by removing electrons from the metal, thereby forming a positive region where an oxide film spontaneously forms. The result is a stable, passive surface with a very low corrosion rate. Ex: Chromate (+6)

__**What is NACE?**__ - NACE International, the National association of Corrosion Engineers. - It is the leader in the corrosion engineering and science community and the largest organization in the world committed to the study of corrosion. - It is recognized around the world as the premier authority for corrosion control solutions. - it was established 1943 by 11 corrosion engineers in the pipeline industry (now 22000 members in over 100 countries.) - It has more than 60 years of experience in developing corrosion prevention and control standards.

George C. Lee and Ernest Sternberg. Issues in Science and Technology, Mar 22, 2008.Retrieved from [] The Birmingham Post (England), Aug 13, 2009. Retrieved from [] R.E. McGuire. The Oil Daily, Mar 25, 1986. Retrieved from [] J. R. Davis, Handbook of Materials for Medical Devices, ASM International, Materials Park, OH, 2003. Retrieved from [] Lee R. Mahoney, "Inhibitor (chemistry)," in AccessScience, ©McGraw-Hill Companies, 2008. Retrieved from []
 * Bibliography**