PhotoNic69 wrote:Caustic soda is really nasty stuff. I've used it quite a bit around the home. You are likely to strip the paint off your frame before the post dissolves.
Have your tried Coca-Cola? (Other brands are available). Fill tube repeatedly with this for a few days . The citric acid should dissolve a lot of the corrosion. My dad used coke on a 150 year old Spanish pistol he found buried in mud. Three days later he got the firing pins to move!!
I use 17p 1l cola from tesco for rust removal, works a treat