Atmospheric corrosion summary

Because cast iron components are normally very heavy in section, the relatively low rates of attack associated with atmospheric corrosion do not constitute a problem and little work has been carried out on the phenomenon. A summary of some of the data available is given in Table 3.42. The most extensive work in this field was initiated by the A.S.T.M. in 1958 and some of the results produced by these studies are quoted in Table 3.43. It will be noted that there is a marked fall in corrosion rate with time for all the metals tested. 

Summary of Atmospheric Corrosion Data. From the raw data we can draw several salient points. 

The rust layer usually consists of dense inner regions of amorphous FeOOFI and crystalline magnetite. The outer layer consists of crystalline a-FeOOH (goethite), y-FeOOFI (lepidocrocite), and y-Fe203 (maghemite) [9]. In summary, atmospheric corrosion of iron occurs in several steps ... 

Table 3 is a summary of commonly used corrodents in laboratory exposures [1]. Methods to generate and monitor the corrodents are also displayed in the table. For several important constituents, no suitable continuous monitoring technique is available. Gaseous chlorine is often used as a substitute for hydrogen chloride, for which there is no simple way of generation. However, the use of gaseous chlorine is debated because of its absence in many important atmospheric environments. It may introduce a corrosion chemistry into the experiments regarded as unrealistic. 

In this chapter, pure and dense P-Sig Al20jN8 2S (z= 1-3) were synthesized by CS followed by SPS without any sintering additives. The Vickers hardness, thermal conductivity, and the corrosion resistance in different atmospheres were investigated for the application as high-temperature engineering materials. In summary, this study introduced an effective method to synthesize pure and dense P-SiAlON materials and showed many valuable property data, which could provide significant references for the application in fields as engineering materials. The content of this chapter is based on the author s doctoral thesis [28]. 

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