corrosion

Corrosion in marine environments

July 14, 2025
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Introduction

Seas and oceans are some of the most hostile environments for engineering materials. Corrosion in marine environments causes billions of dollars in annual damage to various industries, such as shipbuilding, oil rigs, and offshore facilities. This article analyzes corrosion mechanisms in the marine environment, factors affecting it, and preventive solutions.

1. Unique characteristics of the marine environment

The marine environment is highly corrosive for the following reasons:

  • High concentration of chloride  ions: Seawater contains about 3.5% dissolved salts, especially sodium chloride.

  • Dissolved  oxygen: Seawater is in constant contact with the atmosphere and contains a high content of dissolved oxygen.

  • Biopollution  phenomenon: The growth of marine organisms on metal surfaces can cause local erosion.

  • Changes in temperature and salinity  : fluctuations in these parameters in different areas of the sea affect the rate of erosion.

2. Types of corrosion in the marine environment

2.1. Uniform wear

General corrosion of the metal surface that is in direct contact with seawater.

2.2. Galvanic corrosion

When two different metals come into contact in seawater, the metal with the lowest electrical potential (anode) corrodes.

2.3. Point corrosion

Create localized holes on the metal surface, which can be very dangerous.

2.4. Corrosion of cracks

In areas where water flow is restricted, such as under washing machines or fixtures.

2.5. Corrosive corrosion

A combination of mechanical effects (e.g. water flow) and chemical corrosion.

3. Factors affecting marine corrosion

  • Water  depth: Erosion rates are higher in the tidal zone (spray area).

  • Temperature  : As the temperature rises, the rate of corrosion increases.

  • Water  flow rate: Faster water flow exacerbates overall corrosion.

  • Biological  activity : marine organisms can increase or decrease erosion.

4. Materials used in the marine environment

4.1. Carbon steel

The most economical option but requires protective cover.

4.2. Stainless steel

More expensive but has better wear resistance (such as grades 316 and 2205).

4.3. Copper-nickel alloys

Such as Cu-Ni 90-10 alloy for seawater pipes.

4.4. Aluminum alloy

Lightweight and corrosion resistant but with limited strength.

4.5. Titanium and its alloys

Excellent resistance, but expensive.

5. Marine corrosion protection methods

5.1. Protective coatings

  • Organic  coatings: epoxy paints, polyurethane.

  • Metal  coatings: zinc and zinc alloy coatings

  • Metal  coatings: galvanized, metal-plated.

5.2. Cathodic protection

  • Sacrificing anodes: use zinc or magnesium anodes

  • Cathodic Protection Applied  : ICCP System

5.3. Proper design

  • Avoid gaps and sharp corners.

  • The right choice of materials used in galvanic contact

  • Consider accessibility for inspection and maintenance.

6. Specific challenges facing the maritime industry

6.1. Shipbuilding industry

  • Hull corrosion

  • Problems with water balancing tanks

  • Corrosion of impellers and shafts

6.2. Offshore oil platforms

  • Corrosion in the tidal zone

  • Problems with steel foundations

  • Corrosion of plumbing systems

6.3. Coastal facilities

  • Corrosion of steel poles

  • Destruction of reinforced concrete in the marine environment

  • Corrosion of port equipment

7. Marine Corrosion Test and Control  Methods

7.1. Accelerated testing

  • Salt Spray Test

  • Seawater Immersion Test

  • Moisture Drying Cycle Test

7.2. Field monitoring methods

  • Corrosion Potential Measurement

  • Use of wear vouchers

  • Electrochemical methods such as polar resistance

7.3. Periodic inspections

  • Visual inspection

  • Thickness Measurement Test

  • Non-Destructive Testing (NDT)

8. Recent innovations in combating marine corrosion

  • Development of smart coatings with self-healing capabilities

  • The use of nanomaterials in protective coatings

  • Online Corrosion Monitoring Systems

  • Use advanced coating techniques such as HVOF

9. Conclusion

Corrosion in marine  environments is a complex engineering challenge that  requires a systematic and multifaceted approach. Choosing the right materials, designing appropriately, using protection systems, and continuous monitoring are effective solutions to manage this problem. As new technologies evolve, more cost-effective solutions to combat marine erosion are expected to be developed in the future.

10. Sources and references for further reading

  • Millshares, R. (2003). Marine corrosion of steel.

  • ASTM G52 – Standard Practice for Exposure and Evaluation of Metals and Alloys in Shallow Seawater

  • ISO 11306 – Corrosion of metals and alloys – Exposure guidance and evaluation of metals and alloys in marine surface waters

  • Society of Corrosion Engineers (NACE International) Materials