When we bought our boat, the Windline swimstep was rusting and the bolts looked pretty bad. But, there was a sticker on it claiming a Lifetime Warranty so I contacted Windline.
Long story short, they issued me an RMA, I shipped it back at my expense (about $40 - I just dropped it off at a UPS Store and they did everything including the packaging) and a few weeks later I had my swim ladder back and it looked like new. New hardware and all!
Not sure what brand you have, but Windline really backed up their warranty - even knowing this was not new to me and I told them I could only assume the ladder was as old as the boat - 20+ years!
Just an idea.

. Good luck!