Ferric chloride pitting susceptibility

Recommended practice for examination and evaluation of pitting corrosion Test method for determining susceptibility to stress corrosion cracking of high-strength aluminium alloy products Test method for pitting and crevice corrosion resistance of stainless steels and related alloys by the use of ferric chloride solution Recommended practice for preparation and use of direct tension stress corrosion test specimens... 

In a recent investigation of the corrosion resistance of as-welded C-276, C-22, and alloy 686 specimens, Saldanha [47] has shown that such weld metal is also susceptible to rapid and severe pitting in a simulated plant solution, boiling 80 % acetic acid with 1000-5000 ppm ferric chloride. There was severe pitting on all three alloy weldments see Fig. 23 for pitting in C-276 weld metal in only five days of testing. There was no attack in the heat-affected zones or in the base-plate. Thus, there are plant environments in which... 

To evaluate the susceptibility of the cobalt-based eilloys to localized attack, the procedures described in ASTM G 48, Test Method for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by the Use of Ferric Chloride Solution can be used. When tested in 6 % ferric chloride, for example, at a temperature of 65°C, the pit densities and depths for samples of UNS R31233 were less than those for UNS N10276. 

Zirconium is susceptible to pitting corrosion in the presence of halide ions, especially chlorides. In pure hydrochloric acid, zirconium does not undergo pitting corrosion but if the electrolyte also contains ferric or cupric ions, the corrosion potential increases and pitting corrosion occurs. It has, for example, been shown that the presence of 500 ppm Fe -" in 20% HCl at 100 °C induces pitting corrosion in zirconium (Yau and Maguire, 1990). 

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