Corrosion is one of the most important factors governing the life, safety and maintenance cost of ships and offshore structures. This course covers electrochemical corrosion, seawater chemistry, general ship corrosion and localised attack mechanisms. It builds from corrosion electrochemistry and the Nernst equation to the shipboard and localised damage mechanisms that govern inspection, material selection and corrosion control. It explains electrochemical cells, equilibrium potentials, polarisation and corrosion rate, then how seawater composition, salinity, pH, dissolved gases, scale and biofouling influence corrosion risk. It covers passivity and oxygen control, environmental effects and the distinct corrosion zones found on ships, and finishes with galvanic corrosion, pitting and crevice corrosion, intergranular attack, microbiologically influenced corrosion, stray current, erosion corrosion, stress corrosion cracking and hydrogen damage.
Course at a glance: Duration 20 hours · Self-paced online · 7 sections, 22 lessons, a 82-page downloadable course book
What you will learn
- Explain aqueous corrosion as an electrochemical process and relate corrosion current to metal loss.
- Calculate equilibrium electrode potentials with the Nernst equation and interpret mixed-potential behaviour.
- Explain polarisation and how it controls corrosion rate.
- Analyse how seawater composition, salinity, pH, dissolved gases, scale and biofouling influence corrosion risk.
- Explain passivity and oxygen control, and diagnose general corrosion in hulls, ballast tanks and cargo tanks.
- Distinguish galvanic, pitting, crevice, intergranular, microbiological, stray-current, erosion, stress corrosion and hydrogen mechanisms.
- Apply corrosion-rate, Nernst, pH and galvanic calculations to assess corrosion risk in marine structures.
Inside the course: a high-level summary, section by section.
Corrosion electrochemistry
The course begins with corrosion as an electrochemical process. In seawater, a metal such as steel forms anodic sites, where metal atoms lose electrons and dissolve as ions, and cathodic sites, where those electrons are consumed, usually by oxygen reduction. Electrons flow through the metal, and ions move through the seawater to complete the circuit. Faraday’s law relates corrosion current to the mass of metal lost, allowing a measured or estimated current density to be converted into a corrosion rate in millimetres per year.
The Nernst equation calculates the equilibrium potential of an electrode as a function of ion concentration and temperature, and the course explains how potentials are expressed against different reference electrodes, such as the standard hydrogen electrode and the saturated calomel electrode. Polarisation describes how electrode potentials shift when current flows, and mixed-potential theory explains how the corrosion potential and corrosion current are set where anodic and cathodic reactions balance. Activation, concentration and resistance polarisation each limit the corrosion rate in different situations.
Seawater chemistry
Seawater composition varies around the world. Typical open-ocean salinity contrasts with diluted waters, such as the Baltic Sea, and concentrated waters, such as the Arabian Gulf, where evaporation raises salt content. Chloride ions are particularly important because they break down protective films. Dissolved oxygen, which decreases as temperature rises, controls the cathodic reaction, while carbon dioxide hydrates and dissociates to form different species depending on pH. The course explains how pH changes affect corrosion and scale formation, and how calcareous scales and biofouling can either protect a surface or create conditions for localised attack.
General ship corrosion
Passivity is the formation of a thin protective oxide film that dramatically reduces corrosion, and oxygen control can either support or undermine it. Environmental effects, including temperature, flow velocity, salinity and pollution, are discussed. The course then examines shipboard corrosion zones: the external hull in atmospheric, splash and immersed zones, ballast tanks subject to alternating wet and dry conditions and warm temperatures, cargo tanks affected by cargo chemistry and inert gas, and void spaces and double bottoms where coating breakdown may go unnoticed. Understanding these zones underpins coating systems, cathodic protection and inspection planning.
Localised corrosion mechanisms
Localised corrosion is often more dangerous than general corrosion because it can cause perforation or cracking with little overall metal loss. Galvanic corrosion occurs when dissimilar metals are electrically connected in seawater, and the area ratio between anode and cathode strongly affects the rate. Pitting and crevice corrosion attack passive metals, such as stainless steels, where chlorides and oxygen depletion create aggressive local conditions. Intergranular attack occurs along grain boundaries, often after improper heat treatment or welding.
Microbiologically influenced corrosion is driven by bacteria such as sulphate-reducing bacteria, particularly in stagnant water, ballast tanks and pipelines. Stray-current corrosion arises from leakage currents, for example during shore-power connections or welding alongside. Erosion corrosion combines mechanical wear with chemical attack in high-velocity flows, such as pump impellers and pipe bends. Stress corrosion cracking requires a susceptible material, tensile stress and a specific environment, and hydrogen damage, including hydrogen embrittlement from over-protection or welding, can cause sudden brittle failure.
From mechanism to control and inspection
Throughout the course, each mechanism is linked back to the practical decisions it influences. Knowing whether a problem is driven by oxygen supply, chloride concentration, galvanic coupling, bacteria or stress helps engineers choose the right response, whether that is a change of material, a better coating system, cathodic protection, electrical isolation, improved drainage and ventilation, or modified operating practice. It also shapes inspection: general corrosion can be tracked with thickness measurements, while pitting, crevice attack and cracking require closer visual examination and more targeted non-destructive testing, because a few deep defects can matter more than average wall loss.
The assessment structure reinforces this progression. Early sections build the electrochemical and chemical foundations, and later sections ask learners to apply them to shipboard zones and localised mechanisms, so that by the end of the course the theory is firmly connected to real structures, tanks and piping systems.
Why this matters in practice
Corrosion drives a large share of ship maintenance, dry-docking work and structural renewal, and localised attack can cause leaks, pollution and structural failure. Engineers who understand the electrochemical and environmental basis of corrosion can choose suitable materials and coatings, design effective cathodic protection, set sensible inspection intervals and diagnose failures correctly. The quantitative tools, from Faraday’s law to the Nernst equation, allow engineers to estimate corrosion allowances and compare protection options rather than relying on guesswork. For surveyors and superintendents, recognising the signature of each mechanism, such as the shape of pits, the location of cracks or the pattern of attack around a weld or fitting, is the first step towards an accurate diagnosis and an effective repair that does not simply reproduce the conditions that caused the original damage. This knowledge is equally relevant to new design, condition assessment, life extension and accident investigation.
Key takeaways
You leave able to explain corrosion electrochemistry, apply Faraday’s law and the Nernst equation, interpret polarisation, analyse the influence of seawater chemistry, diagnose general corrosion in ship structures and distinguish the main localised corrosion mechanisms and their causes.
How you study
The course is delivered fully online and is self-paced, so you can fit roughly 20 hours of study around professional commitments. Lessons combine clear explanation with examples, diagrams and short interactive checks, and the main sections end with graded quizzes (4 in total) so you can confirm you can apply each method before moving on. A 82-page course book can be downloaded and printed for offline reading and later reference.
Course contents
- Module Context: Course Scope; Assessment Structure
- Corrosion Fundamentals: Electrochemical Cells; Nernst Equation; Polarisation and Rate
- Seawater Chemistry: Seawater Composition; pH and Dissolved Gases; Scale and Biofouling
- General Corrosion in Ships: Passivity and Oxygen Control; Environmental Effects; Shipboard Corrosion Zones
- Localised Corrosion: Galvanic Corrosion; Pitting and Crevices; Intergranular Attack; MIC and Stray Current; Erosion, SCC, and Hydrogen
- Summary: Key Takeaways
Who this course is for
This course is for engineering graduates and practising engineers in naval architecture, marine and offshore engineering, coating and corrosion specialists, surveyors and superintendents responsible for hull and tank condition. A basic background in chemistry and materials is helpful.
Frequently asked questions
How long does Structural and Material Response to the Marine Environment take?
The course is designed for about 20 hours of study. It is self-paced and fully online, so you can spread it over a few weeks or complete it more quickly.
What is covered?
The course is organised into 7 sections with 22 lessons, moving from foundations to applied methods, as summarised above.
Is there material to keep after the course?
Yes. A downloadable 82-page course book accompanies the lessons for offline reading and later reference.
How is progress checked?
Each main section closes with a graded quiz (4 in total). The quizzes test understanding of the concepts and methods explained in the lessons rather than memorisation, and you can review the relevant lessons before attempting them.
Can I record this study for my own professional development?
Yes. The course notebook includes a self-assessment of the course objectives before and after study, a reflection page and a learning log, which you can use to keep your own record of professional development.
Duration: 20 hours
Related courses: C01 – Naval Materials Science and Engineering; C02 – Materials Science for Maritime and Naval Engineering; A10 – Naval Architecture and Ship Production Technology (Part 1 of 4); H01 – Renewable Energy Technologies
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