The effect of the diffusive, composite chromium nitride layers produced by a hybrid surface treatment on the corrosion behavior of AZ91D magnesium alloy

The layers based on chromium nitride were produced on the AZ91D magnesium alloy using a hybrid surface treatment. The treatment consists of nitriding of the chromium-precoated magnesium alloy. The proposed treatment yields diffusive, composite gradient-type chromium nitride layers which are diffusion-bonded to the substrate. The effect of these layers on the corrosion behavior of the AZ91D magnesium alloy was investigated by the potentiodynamic and impedance spectrometry methods. It was found that the formation of the diffusive, composite chromium nitride layers on the AZ91D alloy may result in a significant decrease of the corrosion activity measured by the corrosion potential. This effect is correlated with the layer thickness and becomes significant with relatively thin layers (less than 1 μm thick). Moreover, with the thin layers the impedance modulus is the highest and phase angle has a beneficial character.

► Hybrid method allows to produce diffusive chromium nitride layers on magnesium alloys.
► Chromium nitride layers on AZ91D alloy improve corrosion resistance.
► The best corrosion resistance occur when the CrN layers are sufficiently thin.