From the blog kaesertalksshop
Chemistry and compressed air piping
Piping connections in existing compressed air system are often made simply by putting two joints together, flanged or threaded. However, when it comes to chemical composition, connecting aluminum directly to brass or copper can cause a chemical reaction called galvanic corrosion. Over time electrons are shed from one material to another. This can cause pitting corrosion, even in your new aluminum piping.