Coupon immersion testing remains one of the most common methods of estimating corrosion rates or of making a final evaluation of alloy resistance to an environment. In this test, a metal specimen (coupon) of known dimensions is immersed in a fluid for a specified length of time. The corrosion or penetration rate is estimated from the mass lost during the exposure. The rate is estimated by
(1)
where R is the penetration (corrosion) rate (mm/y), A is the exposed area (cm), m1 and m2 are the initial and final masses (gm), t1 and t2 are the starting and ending times (h), ρ is the density (gm/cm3), and K is a constant for unit conversion.
One question that arises when examining reproducibility of immersion test results...
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