Hydrofluoric acid is a water solution of hydrogen fluoride (HF). Hydrofluoric acid is used widely in diverse types of industrial applications; traditionally, it is used in pickling solutions in the metal industry, in the fabrication of chlorofluorocarbon compounds, as an alkylation agent for gasoline and as an etching agent in the industry of glass. In recent years, hydrofluoric acid has extensively been used in the manufacture of semiconductors and microelectronics during the wet chemical cleaning of silicon wafers. Hydrofluoric acid can be considered a reducing acid and although it is chemically classified as weaker than, for example, sulfuric or hydrochloric acids, it is extremely corrosive. This acid is also particularly toxic and poses greater health hazard than most other acids. The corrosion behavior of metals in hydrofluoric acid has not been as systematic studied in the laboratory as for other common inorganic acids. This is largely because tests using hydrofluoric acid cannot be run in standard equipment and because of the toxic nature of this acid. Moreover, short-term weight loss laboratory corrosion tests in hydrofluoric acid can be frustrating since the results are not as highly reproducible as in the case of other acids such as sulfuric or hydrochloric. One …

Environmentally Assisted Cracking (EAC) is a general term that includes phenomena such as stress corrosion cracking (SCC), hydrogen embrittlement (HE), sulfide stress cracking (SSC), liquid metal embrittlement (LME), etc. EAC refers to a phenomenon by which a normally ductile metal looses its toughness (e.g. elongation to rupture) when it is subjected to mechanical stresses in presence of a specific corroding environment. For EAC to occur, three affecting factors must be present simultaneously. These include: (1) Mechanical tensile stresses, (2) A susceptible metal microstructure and (3) A specific aggressive environment. If any of these three factors is removed, EAC will not occur. That is, to mitigate the occurrence of EAC, engineers may for example eliminate residual stresses in a component or limit its application to certain chemicals (environment). The term environment not only includes chemical composition of the solution in contact with the component but also other variables such as temperature and applied potential. Nickel alloys are in general more resistant than stainless steels to EAC. For example, austenitic stainless steels (such as S30400) suffer SCC in presence of hot aqueous solutions containing chloride ions. Since chloride ions are ubiquitous in most industrial applications, the use of stressed stainless steels parts …