A while ago we bought a very nice set of chairs with a chromed base and the bog standard pneumatic height adjustment.
After a lot of use a couple of them had the welds on the base break apart. I took one home and after thinking a bit I chose to make a stiffening plate instead of just redoing the missing parts as that area looked very flimsy.
I traced the outline on some cardboard and then cut a bit of plate with the plasma torch.
Some light prep and careful welding made it usable again. I tried first with a small 6013 rod but the arc wandered and blew a hole through the thin base. I had more success with 7018. The welds look horrible but are strong enough, I jumped a couple of times and it didn’t even notice.