How to Make Structural Rust Repairs in Buildings
It is important to make rust repairs as soon as it is detected, because it can quickly spread and cause significant damage to the steel or other metal. Rust can also weaken the overall structure of a building, potentially leading to safety hazards. Plus, rust can be unsightly and can affect the appearance of a building.
By repairing rust, it is possible to protect the structural integrity of the steel or other metal, maintain the appearance of the building, and reduce the risk of safety hazards. There are several methods for repairing rust, as mentioned below, and the best method will depend on the severity of the rust and the importance of the steel or other metal in the building. This is where a structural engineer can help.
The options to make rust repairs in building structures include:
Sanding and priming: This method involves sanding down the rust until it is no longer visible, then applying a coat of primer to help prevent the rust from returning. A structural engineer can help provide specifications for this.
Painting: If the rust is not too severe, it may be possible to simply paint over it to help protect the steel from further corrosion. High build epoxy paints generally offer the most durability for up to 25 years before first service, however depends on the location and whether a top coat such as polyurethane or acrylic protective coating is also applied.
Rust conversion: This method involves applying a chemical solution to the rust, which converts it into a stable compound that can be painted over. This is not recommended as a standalone treatment, and generally does not meet Australian Standards as a protective coating in itself.
Rust inhibitors: These products are applied to the steel to help prevent rust from forming in the first place. They are typically applied as a thin coat over the surface of the steel. These are more of a preventative treatment, and requires periodic reapplication unless a more durable protective coating is applied.
Powder coating: This is a process in which a dry powder material is applied to the surface of a metal object and then heated to form a protective and decorative layer. Powder coating can be a good option for repairing steel rust in buildings because it is durable and resistant to corrosion. After preparing the surface, the powder coating material is applied to the surface using a spray gun or other applicator, then cured or heated.
Welding: If the rust is severe and the steel is structurally important, it may be necessary to remove the rust and weld on new steel plates or sections to repair the damage.
Galvanization: This method involves coating the steel with a layer of zinc, which helps to protect it from corrosion. But galvanising is usually limited to shop fabrication for new structural steel.
Stainless steel: If the rust is severe and the steel is not structurally important, it may be possible to simply remove the rust and replace it with stainless steel, which is highly resistant to corrosion. But consideration for passivation is important as dissimilar metals can sometimes accelerate rust.
Other Considerations: Depending on the application,
It is important to note that the best method for repairing steel rust will depend on the severity of the rust and the importance of the steel in the building. It is always a good idea to consult with a professional engineer for specifications or contractor to schedule the most appropriate repair method.
Other Considerations to Prevent Rust
It is important to consider other holistic factors when making structural rust repairs. Such as moisture, salinity, chemicals, and electrolysis that can also contribute to the corrosion of steel and other metals.
Moisture: The presence of water or moisture can accelerate the corrosion of steel and other metals. Water can dissolve many of the compounds that form on the surface of metal and carry them away, exposing the metal to further corrosion.
Salinity: Saltwater is particularly corrosive to metals, especially steel. The salt in the water can dissolve and carry away metal ions, leading to corrosion.
Chemicals: Certain chemicals can also be corrosive to metals, particularly if they are acidic or basic. These chemicals can attack the surface of the metal, leading to corrosion.
Electrolysis: This type of corrosion occurs when two different types of metal are in contact with each other in the presence of an electrolyte (such as water or a salt solution). An electrical current can flow between the two metals, causing one of them to corrode.
Use non-conductive materials to separate different types of metal: If it is necessary to use different types of metal in close proximity to each other, it is important to use non-conductive materials, such as rubber or plastic, to separate them. This will prevent an electrical current from flowing between the metals and causing corrosion.
Cathodic protection: This is a method of protecting metal surfaces from corrosion by using an electrical current to prevent the corrosion reaction from occurring. It is often used to protect metal structures, such as pipelines, tanks, and ships, from corrosion.
There are two main types of cathodic protection: galvanic cathodic protection and impressed current cathodic protection.
Galvanic cathodic protection: This method involves attaching a more electrically active metal, such as zinc or aluminum, to the surface of the metal that is being protected. The more electrically active metal will corrode instead of the less active metal, protecting it from corrosion.
Impressed current cathodic protection: This method involves running an electrical current through the metal surface that is being protected. The current helps to neutralize the corrosion reaction, protecting the metal from further corrosion.
Cathodic protection can be an effective way to prevent corrosion in metal structures. However, it is important to design and maintain the cathodic protection system correctly in order to ensure its effectiveness. For this reason specialist contractors provide these Design and Construct services, and can offer a maintenance schedule with regular intervals to ensure that the system is functioning properly.
To prevent corrosion, it is important to protect metal surfaces from exposure to water, salt, and chemicals, and to use corrosion-resistant materials whenever possible. In addition, it is important to regularly inspect metal surfaces for signs of corrosion and to repair any corrosion that is found as soon as possible.
Regular inspections especially on coastal bridges, culverts and buildings is a good place to start, ideally from an RPEQ Engineer.