Electrochemical Measurements. Applicable QAP’s and IP’s will be used to maintain data accuracy. Accuracy of measurements and data will be determined by comparison with known standards whenever possible. Accuracy of each complete electrochemical test apparatus (consisting of reaction flask, temperature control, gas and electrolyte flow control, counter electrode, and reference electrode) will be determined using ASTM G5, “Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements” [2]. This method uses a standard ferric Type 430 stainless steel (UNS S43000) sample available from ASTM Headquarters. Measured current-potential curves should fall within the limits presented in the ASTM G5 method. Corrective action to the test apparatus will be taken if the system response is outside of the standard limits. A minimum of three points in the conditions test matrices (Tables 1 – 4) will be tested in duplicate, and one point in triplicate, to determine precision. The conditions chosen for duplicate and triplicate testing will be determined during the course of experimentation based on equipment availability and time constraints. Comparisons within data sets and with similar data in the literature will demonstrate representativeness. Uncertainty or scatter can be of the order of a factor of 2 in typical electrochemical data, such as passive corrosion current densities. This uncertainty is acceptable because these parameters will often change by several orders of magnitude as a function of time and metallurgical conditions. Uncertainties are presumably due to the stochastic nature of the metal surfaces and bulk solution properties. Potential sources of error include variation of flow condition of electrolyte, dissolved oxygen content, pH, temperature, surface condition of the working electrode from initial polishing and the effects of the test conditions, etc.; these factors will be controlled and maintained as closely as practical under laboratory conditions. Human error will be minimized by personal qualification requirements, indoctrination, and training. Instrumental error will be minimized by calibration of testing equipment and following the requirements of all applicable IP’s.
