The diameter and average depth of a corrosion pit can be selected.
The figure depicts aspects of an electrochemical cell for pitting-corrosion tests of material specimens. The cell is designed to generate a region of corrosion having a pit diameter determined by the diameter of a selectable tip. The average depth of corrosion is controlled by controlling the total electric charge passing through the cell in a test. The cell is also designed to produce minimal artifacts associated with crevice
There are three selectable tips, having diameters of 0.1 in. (0.254 cm), 0.3 in. (0.762 cm), and 0.6 in. (1.524 cm), respectively. The amount of electric charge needed to generate a corrosion pit having desired average depth h at a selected diameter d is given straightforwardly by
Q = Fρπd2h/(4W)
F is the Faraday constant (the charge of one mole of electrons), ρ is the mass density of the specimen material, and W is the equivalent weight of the material (the mass of one mole of the material divided by the valence of the material).
This work was done by Janice Lomness and Paul Hintze of Kennedy Space Center. For further information, contact the Kennedy Innovative Partnerships Office at (321) 861- 7158.