Scrub away the rust. Use a scrubbing pad or wire brush to scrub away the rust from the metal pole. Use vigorous strokes on the larger areas. Because the metal poles are designed to hold up a barn, they are sturdy, so using force will not cause any structural damage. Wipe away the rust.
Apply lubricant, either WDF-40 or mineral oil, with a scrubbing pad, or you can spray the WD-40 on the rust stains. Allow the lubricant to penetrate the rust stains for about 15 minutes. Scrub off the rust with the scrubbing pad. Use a damp paper towel to clean off the rust and lubricant. Dry the metal pole. Use a lubricant on the stubborn rust stains. Because the metal barn poles stretch the height of the building, a ladder will be needed to remove the rust at higher levels.
Put on rubber gloves and apply naval jelly to the difficult rust stains. Pour a little naval jelly onto a paper towel and then apply the jelly to the rust stains. Wait several minutes for the naval jelly to take effect. Wipe off the rust and naval jelly using paper towels. Wipe the metal pole barn clean and dry. The main ingredient of naval jelly is phosphoric acid, which dissolves rust. Because rust removers are safe for humans to use, the product will not cause problems for the horses.