I am no expert but I had three gates that where my helper grabs them to open, his sweaty hands caused them to rust out bad with holes thru the metal. The rest of the gates were in good shape, so I bought a very fine hard type buffing wheel for a 4" grinder ( Harbor Freight) and buffed over the rust. Then I took some rust stop I bought at Ace Hardware and brushed it over the rusty places. It hardens the rust and bonds it to the metal plus it stops the rusting out. When it dried I painted over it with some implement paint and let it dry. Then I took a piece of thin wall PVC about 18" long and split it down the length on one side only. Then I worked it over the rusted area all the way down until it snapped around the pipe. Took my silicone chalk and seal in both ends of the PVC. Leave split side on underside of gate tubing so water can't collect in it. Siliconed that area also and when it dried, I painted over the PVC to match the color of my gate. This was 5 years ago this July coming and if you don't look for it you don't notice it. Plus it stopped the rusting out for sweaty hands with the pvc covering the tubing.