Should just be able to seal it with any kind of metal sealant tbh mate. You can even use alloy wheel sealant - if you take the word "wheel" out, essentially that's what you've got. Try your Poorboys wheel sealant on it mate
Alot of products double up, but people often don't realise, because clever marketing makes you buy more - like the White Diamond and Black Hole glazes, essentially the ingredients are the same, just the colouring different to entice you to buy twice