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Five stainless steel alloys were tested and compared to find a test method for the qualification of stainless steel used in drinking water systems. Determination of the pitting/critical potentials from the conventional cyclic polarization results was shown to be difficult when stainless steels have high Mo and Cr content. The electrochemical impedance data indicated that results received with the conventional methods do not necessarily reflect the steady state. The low frequency time constant determined from the impedance measurements showed that the anodic polarization should be conducted with very slow scan rate to get information about the mechanism. The steady state investigations were compared with the conventional electrochemical results to propose an electrochemical-based route as a standard qualification method. The qualification method was tested to be valid by a European round-robin-test.
Qualification of materials for use in drinking water applications: Test method for stainless steel
(2007)
Qualification of materials for use in drinking water applications: Test method for stainless steel
(2007)
Geothermal brines often contain high amounts of lead and copper ions that can precipitate as native Cu and Pb as consequence of galvanic corrosion when brines react with carbon steel materials. This contribution evaluates which materials could overcome the problem of galvanic corrosion at geothermal environment.
The behavior of these materials in water containing high chloride concentration (> 100 g/L NaCl) as well as various amounts of dissolved bCl2 and/or CuCl2 was characterized by electrochemical and exposure measurements.
Both methods reveal carbon steel suffers corrosion susceptibility, accompanied by Cu◦ and/or Pb◦ precipitation on the surface. Electrochemical measurements on stainless steels result in significant difference in corrosion and repassivation potentials (Ecorr = -189 mV, Erep = 70 mV), indicating a good corrosion resistance.
Several stainless Steel alloys of interest for drinking water application were tested and compared. EN 1.4404/AISI 316L was used as reference material for round robin test and extended tests representing a wide ränge of conditions in drinking water. The testing procedure was designed to evaluate whether stainless Steel is passive and included a leaching test as well. For thispurpose slowPolarisation (25 mV /1.5 h) was used to show thepassive behaviour of the stainless Steel. Evaluation of the test materials was possible by comparing the dimensions of the passive areas. In the second Step of the procedure, the sample was exposed to a fixed potential, and under this slightly accelerated condition the amount of corrosion products that were leaching was determined. The stability of the test method is shown by a European round-robintest. Results and conclusions for the use of the proposed method for the intended qualification of materials are presented. This procedure was used for the test described in EN 16056 as the qualification procedure for stainless steels. The Application of the procedure for the Evaluation of disinfectants was successfully shown.
