Sandwiched polydopamine (PDA) layer for titanium dioxide (TiO2) coating on magnesium to enhance corrosion protection

• A polydopamine (PDA) layer was inserted into TiO2 coated Mg.
• The sandwiched PDA/TiO2 coated Mg achieved significantly low corrosion current density icorr.
• The sandwiched PDA/TiO2 coated Mg exhibited remarkably suppressed in vitro degradation rate.
• The sandwiched PDA hinders effectively the electrical pathway of galvanic corrosion cell.
• Such kinetic strategy promises a new route for corrosion-control of extremely active magnesium.

A polydopamine (PDA) layer was sandwiched between a TiO2 coating and Mg substrate to enhance the corrosion protection. The PDA layer was covalently immobilized on Mg, and the TiO2 was coated by liquid phase deposition subsequently on it. The hybrid TiO2/PDA coated Mg exhibited significantly smaller free corrosion current density as well as a remarkably lower degradation rate in vitro (up to 21 days) in phosphate buffered saline compared to direct TiO2 coated and untreated Mg. The efficacy is ascribed to the organic PDA layer which suppresses the electric pathway of galvanic corrosion cell and therefore corrosion rate of magnesium.

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