What is the main purpose of using a protective separator when riveting dissimilar metals?

The main purpose of using a protective separator when riveting dissimilar metals is to prevent electrolytic action. When two different metals come into direct contact in the presence of an electrolyte (such as moisture), an electrochemical reaction can occur, leading to galvanic corrosion. This is particularly problematic in applications where dissimilar metals are joined, as one metal will corrode preferentially, which can compromise structural integrity over time.

Using a protective separator can effectively isolate the metals from direct contact, thereby minimizing or entirely preventing this type of corrosion. This protective measure is vital in aerospace and other critical applications where metal integrity is paramount. By preventing electrolytic action, the lifespan of the structure is enhanced, and its performance remains reliable.