Chainmail is compromised and loses much of its protective strength when a link (a ring) is forced open, usually by a piercing attack like a sword- or speartip or perhaps an arrow. A link that doesn't have a closing mechanism that keeps it closed, which would be the rivet, is much easier to force open with an attack, and the whole armor ends up much less protective.

If you're using aluminium, and it's just for a costume and not intended as historical realism, then I suppose you are doing fine.