Applications
Piranha solution is used frequently in the microelectronics industry, e.g. to clean photoresist residue from silicon wafers.
In the laboratory, this solution is sometimes used to clean glassware, though it is discouraged in many institutions and it should not be used routinely due to its dangers. Unlike chromic acid solutions, piranha will not contaminate glassware with heavy metal ions.
Piranha solution is particularly useful when cleaning sintered (or 'fritted') glassware. The size of the pores of sintered glassware is critical for its function, so it should not be cleaned with strong bases, which gradually dissolve the sinter. Sintered glass also tends to capture material deep within the structure, making it difficult to remove. Where less aggressive cleaning methods fail, piranha solution can be used to return the sinter to a pristine white, free flowing form without excessive damage to the pore dimensions. This is usually accomplished by allowing piranha solution to percolate backward through the sintered glass.
Piranha solution is used to make glass hydrophilic by hydroxylating the surface, thus increasing the number of silanol groups on the surface.
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