Ceramics corrosion testing

A hterature review was conducted, which provided some materials as candidates for the section I (Bunsen) of the process ceramics (SiC, Si3N4, AI2O3), glass, fluocarbons, Tantalum and Zirconium or Ni alloys. However, corrosion tests are necessary to assess the maximum temperature and acidity acceptable conditions, the long tenn behaviour and the corrosion mechanisms. 

We are not aware of hot corrosion testing of precursor-derived ceramics. A prediction rests upon the argument that for those which contain boron a top scale compositions in the Na-B-Si-O-system should form, that is a classical glass forming system with low melting points and viscosities [176]. Apart from the hot corrosion degradation by itself it is completely unknown whether this will induce crystallization of the amorphous precursor-derived ceramics. 

While corrosion testing of metallic materials is the focus here, planning and design of environmental perfoirnance tests for nonmetaUic materials, such as paints, plastics, ceramics, and refractories is similar. Specific corrosion test methods have been developed by ASTM International [70-12], NACE International [73], and the International Organization for Standardization (ISO) [74]. 

The test specimens must be physically separated from each other and supported on inert racks. When supported on metal racks the test specimens must be insulated from the metal rack and from each other to prevent galvanic action. Atmospheric corrosion coupons are usually held with ceramic electrical insulators as shown in Figure 15.2. The coupons are usually mounted either at an angle of 20-30 from the horizontal or vertically (see Figure 15.3), Atmospheric corrosion tests usually last at least 1 year and very often extend to 3-5 years. 

Haynes G. In Corrosion Tests and Standards Apphcation and Interpretation, Baboian R., ed. ASTM Manual Series MNL 20, Philadelphia, PA, 19103, 1995, pp. 91-97 Hirai S., Shimakagen K., Aizawa S. Alkaline corrosion resistance of anodised coated with zirconium oxide by a sol-gel process. J. Am. Ceram. Soc. 1998 81(12) 3087-3092 Hirayama R., Harayama S. Electrochemical impedance for degrades coated steel having pores. Corrosion 1991 47(12) 952-963... 

Adams, P. B. 1992. Predicting corrosion. In Clark, D. E. Zoitos, B. K. (eds) Corrosion of Glass, Ceramics and Ceramic Superconductors Principles, Testing, Characterization and Applications. Noyes, Park Ridge, USA, 29-50. 

N. Bonkis, N. Clanssen, K. Ebert, R. Janssen, M. Schacht, Corrosion Screening Tests of High-Performance Ceramics in Supercritical Water Containing Oxygen and Hydrochloric Acid. J. of European Ceramic Society 17, (1997), 71. 

Corrosion resistance testing of ceramics is detailed in the literature.44,45... 

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