Sulfuric acid chromium corroded

Chromium is highly acid-resistant and is only attacked by hydrochloric, hydrofluoric, and sulfuric acids. It is also resistant to other common corroding agents including acetone, alcohols, ammonia, carbon dioxide, carbon disulfide, foodstuffs, petroleum products, phenols, sodium hydroxide, and sulfur dioxide. 

Figure 30 shows an example. The sample is an iron/chromium alloy that had been exposed to an aqueous solution of sulfuric acid. The alloy is covered by a surface layer of approximately one nanometer that consists of oxides and hydroxides of iron and chromium. The composition of the material immediately underneath the passive film equals the bulk composition. This is not always the case, as elements are often depleted underneath the passive film if an enrichment of these elements occurs in the film. Technical problems with this kind of investigation mainly concern the transfer of the corroded sample into the vacuum of the spectrometer. Passive layers that contain hydroxides in solution especially tend to degrade in the vacuum. 

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