Depending on the environmental conditions and cleaning schedule of a facility, it is possible for a barbell to exhibit surface rust.  This is expected more frequently in humid, coastal locations, or facilities that do not follow recommended cleaning procedures spraying cleaner directly on the equipment and leave it to evaporate

• Vinegar: Vinegar is mildly acidic and can help dissolve rust. You can soak a cloth or paper towel in vinegar and wrap it around the rusted areas of the barbell or dumbbell. Let it sit for a few hours or overnight before scrubbing with a stiff nylon brush. Afterward, rinse the barbell thoroughly with water and dry it completely to prevent further rusting.

• Citric Acid Solution: Citric acid, often available in powdered form, can be mixed with water to create a rust removal solution. Follow the instructions on the packaging to create the solution, then apply it to the rusted areas of the barbell or dumbbell. Let it sit for a while before scrubbing and rinsing.

• Commercial Rust Removers: There are many commercial rust removal products available in the market. These products contain chemicals that are specifically designed to dissolve rust. Follow the instructions provided by the manufacturer for the best results. If your barbell or dumbbell hasn't been maintained according to the cleaning guidelines outlined earlier, and if alternative methods have proven ineffective, resorting to a commercial rust remover may become necessary.

• Baking Soda Paste: Baking soda mixed with water to form a paste can also be effective at removing rust. Apply the paste to the rusted areas, let it sit for a while, then scrub and rinse thoroughly.

• Quality oil based lubricant: Quality oil based lubricants not only help loosen rust but also offer some protection against future rusting. Spray Quality oil based lubricant onto the rusted areas, let it sit for a while, then scrub and wipe clean. After using any rust removal method, be sure to rinse the barbell or dumbbell thoroughly with water, dry it completely, and apply a rust inhibitor or lubricant to prevent future rusting. 

Additionally, always follow safety precautions and use protective gear such as gloves and goggles when handling rust removal chemicals.