Carbon steel screws will rust when exposed to moisture unless they are coated with an anti-rust coating or made of stainless steel. However, if the anti-rust coating is worn or chipped due to external factors, thereby reducing its anti-rust strength, rust may occur under the coating. Stainless steel screws are the most resistant to rust and corrosion. Although they are more expensive, their rust resistance is not easily reduced because the entire structure of the screw is stainless steel.