NAVY - MIL-STD-889D
GALVANIC COMPATIBILITY OF ELECTRICALLY CONDUCTIVE MATERIALS
|Publication Date:||21 July 2021|
This standard defines and classifies galvanic compatibility of electrically conductive materials and establishes requirements for protecting electrically conductive materials in a dissimilar couple against galvanic corrosion. Recommendations for protective coatings are provided. This standard also outlines the procedures required to generate electrochemical data for the analysis of new electrically conductive materials, coatings, and surface treatments. Data collected in this standard was completed in static, immersion conditions in artificial seawater in accordance with ASTM D1141 (without heavy metals).
This standard defines and classifies galvanically dissimilar conductive materials and establishes requirements for protecting coupled dissimilar conductive materials against corrosion, with... View More
This standard defines and classifies galvanically dissimilar conductive materials and establishes requirements for protecting coupled dissimilar conductive materials against corrosion, with attention directed to the anodic member of the couple,. Previously, galvanic tables were based solely on the corrosion potentials of the two conductive materials in a galvanic couple. Since the potential difference does not incorporate kinetics, it is recognized that the galvanic potential difference between material couples is not a true indicator of galvanic corrosion. The new methodology incorporated into the "D" revision of MIL-STD-889 is based on the mixed potential theory of electrochemistry that was developed over 70 years ago and validated by electrochemists. Mixed potential theory states that the intersection points of two dissimilar conductive materials polarization curves can be used to determine the galvanic corrosion current and galvanic potential. Instead of crossing the anodic materials curve with the cathodic materials curve, the polarization curves of the anodic and cathodic materials were summed to produce a polarization curve of the joint sample in a 1:1 ratio. The galvanic current and potential obtained from the intersection point of the summed, joint curve can be used to determine the corrosion rate. The data collected in this standard was completed in static, immersed conditions.View Less