ACCELERATED LIFE TESTING

Corrosion Potential Testing (ASTM G 69)

The procedure followed here is as provided in the ASTM method. Samples are exposed to a salt water/peroxide medium along with a saturated calomel electrode. The corrosion potential data, in millivolts, is collected using a PC and used to plot a corrosion potential curve. The brazing industry has a specific not just in corrosion potential, but in the change in potential through the plane of the brazed sheet. The standard practice has been to remove layers of metal by exposure of the aluminum brazing sheet to strong caustic solution and timing the reaction so that only a certain amount of metal is removed. This practice suffers from being uncontrolled and unpredictable. Often the sample was destroyed, thus losing valuable data. Touchstone Research has improved on this method by developing an electro-chemical machining technique for removal of minute amounts of surface material in a predictable manner. Using a DC power source and a copper counter-electrode, the test specimen is suspended in a salt solution while current is passed through the system to remove metal in discrete amounts. As little as 0.0005" can be removed at one step. The sample can then be re-introduced into the test cell and the test continued.

Index of Accelerated Life Testing