Protecting Metal Features on Old Town Homes From Rust and Corrosion
Rust is beginning to show through the silver paint on this gate to a Key West Cemetary plot.
Rust, otherwise known as iron oxide, is formed by the interaction of iron and oxygen molecules in the presence of moisture. Given a long enough time and exposure to the elements, any iron object will eventually convert itself completely to rust. Steel, being comprised largely of iron, is subject to the same process. If salt is present, in sea water for example or road salt, then the corrosion process will be much faster.
Even if the metal is encased in concrete rust can cause a problem. If moisture finds its way in and the steel starts to rust the expansion can cause the concrete to fracture from the inside. This is a common cause of failure in reinforced concrete structures and has even caused problems at the Parthenon in Greece where iron bars were used to strengthen the stonework.
While we won’t find much steel reinforced concrete in Old Town Key West homes, New Town and lower Keys homes will often find this sort of corrosion where iron has been used to reinforce concrete block homes. This was a particular problem in concrete structures where salt water was used to mix concrete – a practice that remained in the 1960s even though fresh water was available from the mainland.
Intricate wrought iron gate has been protected with white paint.
And even in Old Town today we find metal on intricate wrought iron gates like the one on the Angela Street home to the right, metal sculptures or other features that that adorn our gardens.
So how do you prevent rust from damaging or even destroying your metal or reinforced structures? Leaving aside specialist materials like stainless-steel, there are a number of methods that can be applied at the production stage. The key is to protect the surface of the metal to prevent rust from starting. One of the most common methods of doing this is galvanising. This involves coating the steel with a layer of zinc, either by dipping or electroplating. Zinc is cheap and still provides a degree of protection even when the surface is damaged.
For structures that are underground or immersed in water there’s the option of cathodic protection. This works by putting an electrical charge through the metal that inhibits the corrosion process.
Get Your Coat
The most common method of preventing rust, however, is via coatings and paints. These effectively seal the surface of the metal to prevent it from being affected by moisture and air. Temporary treatments such as a layer of oil or grease are often used to protect metal items in transit.
When it comes to permanent rust proofing the most common approach is to make sure the surface is properly protected with paint. Preparation is the key here and any existing rust should be removed beforehand otherwise you’re merely delaying the problem. A good coat of paint should protect the metal for several years. However, it’s important to check for damage periodically and carry out any repairs or touch in damaged areas as soon as possible. If you allow rust to get a hold it can spread beneath the paint and cause flaking which will lead to a much larger area of corrosion. If you catch the problem early you can prevent the damage from becoming too severe.
When considering a permanent treatment it’s important to remember that you need to protect enclosed cavities as well as the external surface. Rust can develop in these areas and by the time you become aware of the problem, it could already be too late. Modern wax-based products can be injected into cavities; they’re designed to penetrate into seams and corners leaving a protective film. They’ll usually have a corrosion inhibitor to stop existing rust too. Because of the wax content the coating remains flexible so that it can cope with minor damage and chips without harming its protection. You can get external coatings that work in a similar way too, remaining flexible below the surface so that they can creep to cover any minor damage.
If rust has already started there are rust proofing products available to treat it. Again it’s important to tackle the problem early and protect any repairs with an appropriate coating or paint them as soon as possible.
Rust is the enemy of all iron and steel surfaces but if you tackle the problem in the right way you can ensure that the metal is protected and will last for many years. The harsher the environment it’s exposed to, the better the protection you’ll need. Prevention is of course better than cure but if it’s tackled early existing rust can be treated effectively.