Degradation of Mg-rich primer (MgRP) during constant immersion in 1 wt% NaCl solution and in dilute Harrison’s solution was compared. The effects of different ions, Mg pigment connection modes, and cathodic reaction sites on the degradation of MgRP were discussed. In addition, an in situ method for the estimation of remaining Mg pigment content in MgRP was developed based on H2 volume collection. The estimation confirmed that there was still Mg pigment preserved in MgRP for continued protection of Al alloy 2024-T3 even though the open-circuit potential (OCP) of MgRP had risen above the OCP of bare AA2024-T3 substrate.

Subject
Scanning electron microscopy, Primers, Pigments, Substrates, Magnesium alloys, Impedance, Corrosion products, Constants, Sodium chloride solution, Magnesium-rich primers, Immersion, Aluminum alloys, Electrolytes
Keywords:
cathodic protection, hydrogen evolution, magnesium-rich primer, microstructure, open-circuit potential
© 2017, NACE International
2017
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