Galvanic corrosion
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JAKOB ALBERTSEN KOMPOSIT A/S
Galvanic Corrosion – Causes, Mechanisms and Protection
Galvanic corrosion is an electrolytic process that occurs when two dissimilar metals are in electrical contact in a conductive environment, such as moisture, salt water or chemical fluids. This form of corrosion can lead to accelerated material degradation of the less noble metal and is a significant challenge in offshore, marine, industrial and pipeline applications.
How does galvanic corrosion occur?
Galvanic corrosion occurs when three conditions are met:
1. Two dissimilar metals are in electrical contact – For example, aluminum attached with stainless steel fittings or a steel bolt mounted in copper.
2. The metals have different electrochemical potentials – The greater the difference in the position of the metals in the galvanic series, the faster the least noble metal will corrode.
3. An electrolytic medium is present – Typically moisture, salt water, acids or chemicals that create an ionic conducting connection between the metals.
The galvanic series – which metals corrode faster?
Metals are divided into a galvanic series, which indicates their electrical potential in a given environment. The further apart the metals are in the series, the greater the risk of galvanic corrosion:
Noble (cathodes – less prone to corrosion)
- Graphite
- Gold, platinum
- Titanium
- Stainless steel (passivated)
- Silver
- Copper, brass, bronze
- Nickel
- Steel, iron
- Aluminum
- Zinc
- Magnesium
Base metals (anodes – corrodes faster)
Example: If aluminum and stainless steel are in contact in a saltwater atmosphere, the aluminum will act as an anode and corrode quickly.
JAKOB ALBERTSEN KOMPOSIT A/S
Methods of protection against galvanic corrosion
To prevent or minimize galvanic corrosion, several strategies can be used:
1. Material selection and galvanic compatibility
- Use metals with similar electrochemical potential, such as aluminum with zinc-plated fasteners instead of stainless steel.
- Avoid direct contact between strongly dissimilar metals, such as copper and aluminum.
2. Insulation between metals
- Use plastic or rubber insulators, washers, or spacers between metal components to prevent electrical contact.
- Use coatings or anodizing to isolate the surfaces from each other.
3. Surface treatment and anti-corrosion coatings
- Use epoxy, polyurethane or zinc-containing coatings to protect the least precious metal.
- Avoid protecting only the cathode (the most noble metal) as this can accelerate corrosion of the anode material.
4. Cathodic protection
- Sacrificial anodes (e.g. zinc or magnesium anodes) can be installed to sacrifice themselves in place of the least noble metal.
- Impressed current systems (ICCP) can be used in industrial and offshore environments to control voltage potential and prevent corrosion.
5. Control of electrolytic environment
- Reduce moisture and condensation through proper ventilation and drainage.
- Limit salt or chemical exposure by using water-repellent coatings or corrosion inhibitors.
- Use corrosion inhibitor additives in coolants or process fluids to neutralize ionic conduction.
JAKOB ALBERTSEN KOMPOSIT A/S
Examples of galvanic corrosion in practice
✔ Shipbuilding: Aluminum hulls rust faster near stainless steel fittings.
✔ Building structures: Steel bolts in contact with copper plates can lead to faster degradation of the steel.
✔ Pipelines: Copper and steel pipes in the same piping system can accelerate corrosion of the steel.
✔ Offshore installations: Steel structures exposed to salt water can be protected with sacrificial anodes.
Galvanic corrosion and ISO standards
Several international standards regulate the control and prevention of galvanic corrosion:
- ISO 12944 – Corrosion protection of steel structures, including material combinations and coatings.
- ISO 9223 – Classification of corrosive environments affecting galvanic reactions.
- ISO 8044 – General concepts and definitions in corrosion technology.
Effective protection with Jakob Albertsen Komposit A/S
At Jakob Albertsen Komposit A/S we offer advanced solutions for the prevention and management of galvanic corrosion, including coating systems, material selection and cathodic protection. Our expertise ensures that your structures receive the best possible protection in demanding environments.
Contact us for advice on how you can prevent galvanic corrosion in your projects.
Do you have any questions or would you like a non-binding offer?
Contact us today for competent sparring and advice on your assignment.
JAKOB ALBERTSEN KOMPOSIT A/S
Contact us for advice on tank coating
Do you need professional tank coating in Denmark or internationally? We are ready to provide technical advice, assessment of your tanks and a non-binding offer. You can contact us by calling +45 62 20 20 58 or sending an email to mail@jakob-albertsen.dk .
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