Overview of EP33CLV
Master Bond EP33CLV is a two-part, room-temperature curing epoxy system suitable for a variety of bonding, sealing, coating, and encapsulation applications. It shows excellent high-temperature resistance and bonds well to a variety of substrates. EP33CLV is also electrically-insulating, making it suitable for encapsulating materials such as Mg alloys to inhibit galvanic corrosion in composites.
Application
Both carbon fiber-reinforced composites (CFRCs) and Mg alloys are promising lightweight materials that can be used to form composites to replace steel parts in automobiles. However, it is difficult to find a machining technique suitable for processing both simultaneously, so their composites are often fabricated by bolting these individual components together. Bolting is performed using steel bolts and washers, but Mg readily forms galvanic couples when it contacts such metallic components. To mitigate galvanic corrosion, an electrically insulating material (such as a polymer resin or polymer tape) can be placed at the interface between Mg and other composite components.
Researchers at Oak Ridge National Laboratory investigated a method to inhibit galvanic corrosion between AZ31B Mg alloy and other components of lightweight composites. As part of the experiments, a layer of Master Bond EP33CLV was used to prevent AZ31B Mg alloy from contacting other composite components, including an SS316 washer and CFRC.
Key Parameters and Requirements
The researchers prepared bolted joints of AZ31B Mg alloy and a CFRC, in which AZ31B directly contacted the CFRC and SS316 washer. To inhibit the galvanic paths in Figure 1a, the authors placed a 200 µm thick layer of EP33CLV onto the top (contact with ss316 washer) and bottom (contact with CFRC) surfaces of the AZ31B surfaces around the pilot hole. This was followed by the application of a low-viscosity epoxy-acrylate resin to heal any microcracks that might develop due to pre-drilling. Finally, PTFE tape was used to wrap the threaded sections of the steel bolts to prevent contact between AZ31B and the Zn-coated steel bolt.
Download the full case study to see the schematics and results conducted by Oak Ridge National Laboratory.
Download full case study
Reference
1Jun, J.; Lim, Y. C.; Li, Y.; Warren, C. D.; Feng, Z. Mitigation of Galvanic Corrosion in Bolted Joint of AZ31B and Carbon Fiber-Reinforced Composite Using Polymer Insulation. Materials (Basel) 2021, 14 (7), 1670. https://doi.org/10.3390/ma14071670.