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Corrosion Testing of Refractories and Ceramics

الكلية كلية هندسة المواد     القسم قسم البوليمرات والصناعات البتروكيمياوية     المرحلة 3
أستاذ المادة قتيبة حسين محمد المرزوكي       6/11/2011 11:44:21 AM

Corrosion Testing of Refractories and Ceramics

 

A. INTRODUCTION

In an echo to Lord Kelvin, who said, "When you cannot measure what you are speaking about or cannot express it in numbers, your knowledge is of a meager or unsatisfactory kind," much effort has been expended in developing tests to measure the corrosion resistance of refractories under slagging conditions and of structural ceramics under hot gas corrosion and oxidation at high temperatures, especially for non-oxide materials. Numerous methods have been tried and some reasonable correlations have been obtained for very specific conditions, but very few methods have reached the status of standard operating practices and none have yet been accepted for universal use. The main reason is that corrosion resistance data obtained in a laboratory environment very rarely simulate the conditions that prevail in service: sample size and geometry, state of stresses in the lining, thermal gradient and thermal cycling, as well as time, which are very difficult to be scaled down to fit with acceptable laboratory test conditions. It must always be remembered that accelerated tests, specially those done using very severe conditions, can lead to erroneous predictions.

Compared with laboratory testing, field-trial testing is, of course, much more costly, and, in some instances, unsafe. It may then be worthwhile to test small panels rather than to carry out full-size testing; the larger the installation the more confidence one will have in the selection of the proper material to use. Postmortem examination of in-service trials also provides very useful insight ts to understand and determine the controlling mechanisms in the degradation of ceramics. Detailed investigations include the use of a wide variety of characterization methods, including chemical analysis, X-ray diffraction, mineralogical analysis, and scanning electron microscopy (SEM)/energy dispersive

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