Instead of taking the frame to the tip, you could try this, which works a treat. Wire brush the frame to remove loose rust, and rust flakes. Then paint it with Hammerite's Kill Rust, which stops the rust eating into the frame. Then paint the frame with Hammerite which is touch dry in half-an-hour. Black or White giving really good results, but there are other colours. I have used this on 50 year old garden gates, which are still going strong. Well worth a bit of effort to restore your picnic table, and also do your bit for the environment, by keeping the frame out of the landfill.