Galvanic corrosion, also known as bimetallic corrosion, is an electrochemical process that occurs when two different metals come into contact in the presence of an electrolyte. This phenomenon is characterized by the accelerated corrosion of the more reactive metal, called the anode, while the other metal, the cathode, remains relatively intact. The flow of electrons from the anode to the cathode in a galvanic cell triggers oxidation and reduction reactions that degrade the anode. This type of corrosion can cause significant damage, leading to substantial economic impact due to repair and maintenance costs, making it crucial to address the issue during the design phase.

The primary cause of galvanic corrosion is the potential difference between the involved metals. Each metal has a specific electrode potential in an electrolyte. This potential difference facilitates the flow of electrons from the more reactive metal to the less reactive one, resulting in the corrosion of the anode. Factors such as the nature of the metals, the composition of the electrolyte, temperature, and the presence of oxidizing agents influence this process. Marine and industrial environments, with high humidity and contaminants, can significantly increase the rate of corrosion.

To mitigate galvanic corrosion, it is essential to implement strategies that reduce or eliminate the contributing factors. Using non-conductive materials between the metals in contact can interrupt the flow of electrons, preventing oxidation and reduction reactions. This isolation can be achieved with bushings, washers, gaskets, and polymer or elastomer coatings, as seen in the oil and gas industry, where epoxy reinforced with glass gaskets are used. It is also crucial to isolate the electrolyte using water-repellent barriers like paints, coatings, oils, and greases that protect the metal from direct contact with the electrolyte, particularly effective in marine or industrial environments.

Additionally, selecting metals with similar electrode potentials can minimize the potential difference and, hence, the corrosion. Consulting the galvanic series ensures that the selected metals are close in terms of their electrode potential. Corrosion inhibitors, chemical compounds added to the electrolyte, can reduce the rate of chemical reactions that cause galvanic corrosion by removing dissolved oxygen from the solution. It is also important to consider the ratio between the cathode and anode areas, as a larger cathode area relative to the anode accelerates the corrosion of the latter. Designing systems where the anode area is larger than the cathode area can reduce the severity of corrosion, such as using steel fasteners in an aluminum structure instead of aluminum fasteners in a steel structure.

Understanding and applying these preventive measures during the design phase is crucial to prolong the lifespan of metallic structures and components, significantly reducing maintenance and repair costs due to galvanic corrosion. These strategies improve the durability of materials and contribute to sustainability and economic efficiency in various industries.