Corrosion is an important consideration for those working within the marine industry.
What is Corrosion?
Corrosion is the process of a refined metal being naturally converted to a more stable form such as its oxide, hydroxide or sulphide state – leading to the deterioration of the material.
Why is Corrosion Protection Important in the Marine Industry?
The marine environment is harsh, with high levels of salt and moisture, making ships and other metallic infrastructure prone to corrosion. When left unattended, corrosion can weaken the construction of ships and structures, in turn raising safety issues and calling for expensive repair work. Generally speaking, the marine and shipping industries utilise mild steel as the preferred material for construction due to its affordability, mechanical strength and ease of fabrication. A few common issues with mild steel is that it corrodes relatively easily when in contact with the harsh marine environment and loses strength quite fast if not properly protected. According to research conducted by the National Association of Corrosion Engineers (NACE) International, corrosion is estimated to cost the global marine sector between 50 to 80 billion dollars annually.
Causes of Marine Corrosion
The universally present high salt content within the air and seawater in the marine environment acts as a corrosion catalyst for ships and offshore structures. Corrosion damage within these environments is generally influenced by the presence of other chemicals and pollutants in seawater, the air and ports. The chemical and electrochemical reactions leading to corrosion are also impacted by additional factors, including:
- Dissolved gases present in seawater – particularly dissolved oxygen
- Sulphate-reducing bacteria causing anaerobic steel corrosion
- Carbonate scale built up on the surfaces being corroded
- Carbon dioxide impacting the pH value of the water
- Climatic conditions of the marine environment
- The electrical conductivity of seawater
- Marine life and bacteriological activity
- Coastal pollution
How To Protect Ships & Structures Exposed To Marine Environments
Manufacturers and operators within the industry take various precautions to protect their vessels and offshore structures from corroding. We will explore some of the standard methods utilised to protect metallic structures in the marine environment.
Design
Ship and infrastructure designers and operators make an effort to reduce corrosion and keep them secure, which aids in extending the lifespan of the structure or vessel. A few design features can assist in reducing the rate of corrosion and in turn reducing the required maintenance costs, including:
- The placement of drains aids in the draining of water from decks, wells and low-lying areas. This eliminates a direct cause of corrosive activity.
- In an effort to reduce galvanic corrosion, insulation is set up in areas where different metals are placed close to one another. Impressed current systems that monitor corrosive cell activity and apply currents to protective anodes can be installed to detect and manage corrosion.
- Insulation is required in locations where temperature shifts, stopping thermal fatigue.
Coatings
An effective way to protect metal structures and ships in the marine environment is by applying coatings to the surfaces. Specialised paint coatings act as a barrier between the corrosive environment and the metallic surface. This is particularly important for surfaces that are in direct and constant contact with the water and sea atmosphere. The coating adds an additional layer of protection, preventing moisture and salt from coming into direct contact with the surface which reduces the likelihood of corrosion occurring.
Coatings also act as an anti-fouling agent, preventing sea life such as algae and molluscs from attaching to the surface, which may expose the metal and increase the rate of corrosion. These coatings also provide a smooth surface helping to reduce drag and resistance for ships, leading to increased fuel efficiency.
Corrocoat and the Marine Industry
Corrocoat has developed product lines that ensure they offer superior corrosion resistance for equipment and infrastructure surfaces exposed to harsh marine environments. With the right protective coating, seawater is not aggressive – our coatings withstand long-term exposure to high levels of salt for extended periods. Corrocoat has provided coatings for various marine industry applications, including Australian Navy vessels and Queensland coast guard boats.
For a wide range of application purposes, Corrocoat has developed new products that will guarantee an increased life expectancy of surfaces. These products provide long-term protection in excess of 25 years when applied directly.