The effect of a zirconium (Zr)-based pretreatment on interfacial bonding properties of a fusion bonded epoxy (FBE) coating on carbon steel is investigated. The initiation and kinetics of delamination of epoxy coatings applied on differently pretreated carbon steel surfaces is studied with scanning Kelvin probe (SKP). In-situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is applied to study interfacial coating-oxide chemistry changes upon electrolyte diffusion towards the buried interface. Corresponding coating degradation is analyzed with the use of electrochemical impedance spectroscopy (EIS). pull off experiments showed a clear beneficial effect of the Zr-based pretreatment improving the dry and wet adhesion properties of the fusion bonded epoxy coating to the carbon steel surface particularly upon exposure to wet and corrosive conditions. This increase in interfacial bonding stability is confirmed by the ATR-FTIR and EIS experiments and delayed and slower delamination was observed in the SKP measurements.

This work studies the influence of the microstructure on the corrosion mechanism and susceptibility of as-brazed aluminum sheet. Various microstructures are obtained using postbrazing heat treatments developed to enhance the corrosion resistance of an AA4xxx/AA3xxx brazing sheet. The heat treatment results in a decrease of the matrix Si content within the heat affected zone and an increase of the Si fraction in the α-Al(Fe-Mn)Si phase. Additionally, the effect of the heat treatment on the local electrochemical activity and corrosion properties are studied. The results indicate that the corrosion susceptibility of the as-brazed structure is diminished resulting from of an amendment of the local electrochemical behavior of the outer clad surface after the post-brazing heat treatment. Moreover, the potential difference between the clad material and core is increased, resulting in an improved sacrificial cathodic protection of the core by the re-solidified clad layer.