Sturdy bits of angle iron (Leasgill LA7)

My knee-high vegetable raised beds are bellying out alarmingly along the sides. This is a result of economising on the thickness of the wooden planks and the tanalised 2x2 posts used for the verticals beginning to rot. I fancy trying bits of heavy duty angle or square/rectangular section to hold the raised beds together a bit more effectively. Would need to be a metre long to be any use. I could easily use a dozen or more, he added hopefully.