How to Stop Rust

Q. We make automated pay stations for parking lots, the machines that allow the customer to pay at the exit with a credit card or cash. We have had some problems with rust breaking out of the seams at the base and around the door panels that provide access to the interior of the machine. The machine works fine but customers are not happy with visible rust. We have tried to apply more coating but it will not penetrate the tight creases in these areas. We also have rust on the edges of the door frame and the door. What can we do to avoid this problem?

A. As you know, “Rust Never Sleeps.” The areas that are causing you trouble are the areas where you do not have any coating or not enough coating to prevent moisture from getting to the steel and causing oxidation. This can be prevented by changing the design or adding a lot more coating to the affected area. It is hard to just add more coating to bridge over a sensitive area. Sharp edges are hard to cover and you cannot get powder down into tight spaces between layers of metal.

The first and most critical thing you should do is to look over the product design and see where the coating may be light or non-existent. If you have overlapped pieces of metal that can allow moisture to run in between the overlapping area, you have a big problem. Look at that design issue; can you seal that area to prevent moisture from getting in between the sheets of metal? Can you redesign to eliminate the overlap? Can you find a way to coat it before you put the two pieces of metal together? Maybe use corrosion-resistant substrate in that area such as galvanized steel or plastic. Any way you choose to address it, you must prevent moisture contact with unprotected (uncoated) steel. If you have any areas where water or humidity can get and powder cannot penetrate, you will have rust. If you have sharp edges, you should change the design to create a radius that will allow a better layer of coating.

Concentrate on a common sense evaluation. If an area can allow water in but cannot be reached with the powder coating, you have to change the design.