Understanding the corrosion resistance of nanocrystalline materials electrochemical influences

YING andL. LI, Chinese Academy of Sciences, China 

Key words nanocrystalline materials, electrochemical corrosion, passivation, semiconductive properties, pit initiation and growth. 

Corrosion is a problem of unassailable importance for the human race, one that exists in every aspect of living. Corrosion can not only cause huge losses for industry, but can also threaten the safety of people s hves and property. Therefore, corrosion is a serious scientific problem. Researchers not only study the corrosion behavior of metals/alloys in various environments, they also analyze the corrosion mechanism and aim to find the most effective ways of protecting materials. 

Nanociystallization has become a useful means of improving the performance of materials. Nanocry stallirre (NC) materials are characterized by their small grain sizes ( 100 nm) and high volume fraction of grain boundaries, which often give rise to unique physical, chemical and mechanical properties compared with those of their cast courrterparts. These properties have been found to be particularly useful for corrosiorr protectiorr applications. 

In the case of normal-temperature corrosion, nearly all metals/alloys are thermodynamically reactive in most natural enviromnents, for example in air. This is especially trae when the environment is moist, polluted or hot, and in water, especially when it is saline, acid or alkaline. There are various common corrosion behaviors of metals/alloys, the familiar patterns among which are active dissolution, passivation and local corrosion. This review focuses on three kinds of corrosion behavior and discusses the effect of nanocrystallization in a liquid system. NC materials have many useful applications and therefore better understanding of their stractural and chemical characteristics is of vital importance. 

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Understanding the corrosion resistance of nanocrystalline materials electrochemical influences... 

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