INTRODUCTION
Zirconium exhibits excellent resistance to most organic environments. To maintain this resistance, it is necessary to have sufficient amounts of water in certain environments. When the water content is insufficient, corrosion problems, such as stress-corrosion cracking, pitting, intergranular attack, high corrosion rate and hydriding, may occur. Yet, there is no report in the public domain on the crevice corrosion of zirconium or any passive alloys in water-deficient organic environments. Zirconium's vulnerability in water-deficient organics results from its need for water to repair any damaged sites occurring in the passive film. When there is not sufficient water for maintaining the passivity, corrosion problems may occur. Accordingly, corrosion problems for zirconium should also include crevice corrosion since the water content is low within a crevice too. Only, crevice corrosion is a very slow process. When the conditions favor the occurrence of corrosion problems outside the crevices, there won't be sufficient time for the development of crevice corrosion. When process conditions are not severe enough to readily attack zirconium, then there is the needed time for crevice corrosion to initiate and propagate. Incubation time for the initiation of crevice corrosion may be long because of zirconium's potent capability to passivate. Though, propagation rate is expected to be fast when zirconium's underlined reactivity is exposed. A model is established to implicate the capability of water-deficient organics to induce crevice corrosion in zirconium. Stainless steels and titanium are included in discussing the applicability of this model to other passive alloys. The factors affecting the crevice corrosion are discussed. Preventive measures are suggested
The performance of metallic materials in organic environments has not been investigated as extensively as that in aqueous inorganic environments. On one hand, in water-rich environments, organic acids attack most alloys similarly to inorganic acids. On the other hand, the corrosion behavior of metallic materials in water-free or water-deficient organics is not straightforward and can be complicated. This paper deals with the crevice corrosion of zirconium in water-deficient organics. Water is a critical component in most corrosion reactions occurring in organic and inorganic environments. It is vital in aqueous corrosion. It usually increases the corrosivity of a given environment and promotes corrosion in most cases. Consequently, dry and water-deficient organics are easily underestimated as corrosives towards metallic materials. In fact, certain dry organics can be highly corrosive. For example, alkyl and aryl halides may quickly react with reactive metals to form organometallic compounds under water- and oxygen-free conditions. The reactivity of organic halides toward metals has been known for more than 150 years. Edward Frankland prepared diethylzinc directly from zinc and ethyl iodide in 1848.1 Conversely, water can be the oxygen source for passivating passive alloys. In this case, water becomes the corrosion suppressor. The focus of this paper is on the corrosive effects of certain water-deficient organics on zirconium. Under water-deficient conditions, corrosion problems may occur when the passivity of zirconium is not well maintained.