Improved Corrosion Resistance of Aluminum Brazing Sheet by a Post-Brazing Heat Treatment

Abstract

This work studies the influence of the microstructure on the corrosion mechanism and susceptibility of as-brazed aluminum sheet. Various microstructures are obtained using post-brazing 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 (HAZ) 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 due to 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 resolidified clad layer.

Electrochemical profiling of multi-clad aluminium sheets used in automotive heat exchangers

“…This corrosion is enhanced by diffusion of Si from the AA4xxx clad after brazing [21,22]. Afshar et al [23][24][25] studied the microstructure and electrochemical behaviour of brazed clad AA4xxx/AA3xxx sheets and observed that the presence of α-Al(Fe,Mn)Si intermetallic phases up to a depth of 5 µm below the surface sheet support galvanic coupling with the internal layers and enhance dissolution and IGC attack. It was postulated that elimination of these corrosion susceptible sites would improve corrosion performance.…”

The Dependence of Microstructural Evolution and Corrosion Resistance of a Sandwich Multi-Layers Brazing Sheets on the Homogenization Annealing

“…Several studies have focused on the corrosion behavior of Al brazing sheet material. Afshar et al found that α-Al(Fe,Mn)Si particles on the surface will increase the cathode current density of the re-solidified clad [15], [16]. Copper was added to the core of brazing sheets, which greatly improves the corrosion life of the material [17].…”

Corrosion Resistance Test of Electroplated Gold and Palladium Using Fast Electrochemical Analysis

“…This approach is commonly used for high-impedance coatings like organic layers [9] and uncoated passivated metals (Ti, Ni, Al, Zn) [10][11][12][13] but no study has been carried out on noble metallic coatings. For this reason, we use methodology that combined the studies on insulating coatings and uncoated metals [14][15][16][17][18][19][20], to obtain a faster, alternative, non-visually destructive, quantitative and modulable method for the evaluation of corrosion of metallic coatings, compared to the current methods used in the galvanic industries. In this study we explore EIS as well as the open circuit potential (OCP) and the corrosion current measurement under an applied stress potential to find the best option for the corrosion strength analysis of noble galvanic coatings.…”