Corrosion removal methods from rusted steel bar

Corrosion removal methods from rusted steel bar

                                                     Chadaram Apparao

Corrosion removal from rusted steel bars is crucial for restoring the material's integrity. There are methods focus on both chemical and mechanical approaches to efficiently clean the bars while minimizing damage. Here are some of the most effective and up-to-date corrosion removal techniques:

Traditional methods

1.    Acid pickling: Acid pickling is a chemical process used to clean rust and scale from steel bars. It involves immersing the steel in an acidic solution, commonly hydrochloric or sulfuric acid, to dissolve corrosion products. This method ensures a clean surface for further treatments like coating or galvanization. But many places it was banned in industrial / large scale usage due to environmental pollution.

2.    Mechanical de scaling: (Sandblasting, Shot Blasting, and Wire Brushing)

       Sandblasting: Uses high-pressure air with abrasive material to remove rust and clean the    steel surfaces. It's effective for heavy rust and prepares the surface for recoating.

      Shot Blasting: Similar to sandblasting, but using metal shot, it is useful for tougher steel bars that need both rust removal and surface strengthening.

     Wire Brushing: This manual or powered method is used for less severe corrosion, ideal for smaller areas or when more control is needed.

     Bending  in reverse direction removes surface scale especially during wire drawing  process.

These processes physically strip rust and contaminants from the surface, preparing the steel for further processing or coating. It’s efficient for heavy corrosion and restores surface integrity.

   3. Chemical Treatments (Rust Converters and Inhibitors)

Rust Converters: These chemicals, typically based on tannic acid or phosphoric acid, react with rust to convert it into a more stable, non-reactive compound (like iron phosphate). This process stops further corrosion and primes the surface for painting or coating. Corrosion Inhibitors: Applied after rust removal, these chemicals prevent future rust formation by forming a protective layer on the steel. Common inhibitors are amines or carboxylates.

 4. Hydro Jetting (Water Blasting)

High-pressure water jets can effectively remove rust from steel bars, especially in larger industrial settings. Hydro jetting is environmentally friendly as it avoids chemical use, and it can reach areas that may be hard to access with mechanical methods.

Modern methods

1. Electrochemical Methods (Cathodic Protection and Electrochemical Realkalization)

Catholic Protection (CP): Involves applying a current to the steel bars, making them the cathode in an electrochemical cell. This method halts the corrosion process by preventing oxidation. It's widely used in reinforced concrete structures, especially where access for physical cleaning is difficult.

Electrochemical Realkalization: Specifically for steel bars embedded in concrete, this method raises the pH around the steel to restore the protective oxide layer and stop ongoing corrosion.

2. Laser Cleaning

Laser technology offers a precise and non-abrasive method to remove rust without damaging the underlying steel. Laser beams are directed at the rusted surface, vaporizing the rust without using chemicals. This technique is gaining popularity for its efficiency and minimal environmental impact.

3. Ultrasonic Rust Removal

This technique uses high-frequency sound waves to remove rust by causing cavitation bubbles that collapse and dislodge rust particles from the steel surface. It's highly effective for detailed or sensitive applications where other methods might damage the material.

4. Plasma Cleaning

Plasma cleaning utilizes ionized gas to remove surface contaminants, including rust. It’s less common than laser cleaning but is effective in applications requiring high precision, such as aerospace or advanced manufacturing.

Each method has its own advantages depending on the extent of the corrosion, accessibility of the bars, and the required surface finish. For industrial or structural applications, methods like laser cleaning, chemical treatments and mechanical abrasion are most common. In more sensitive environments, ultrasonic and electrochemical methods are preferred