• Identify the potential electrical hazards

• Understand the common hazards and electrical safety precautions

• Explain the various corrosion processes

• Describe methods for the prevention of corrosion

Electrical shock is a serious and sometimes fatal physical injury caused by an accidental flow of electricity through the body.

Most injuries from electric shock occur through accidental contact with an exposed wire or other part of a live electrical circuit such as electrical wiring or parts of an electrical appliance. 

Most cases of accidental electric shock involve a hand or arm in contact with a power source. Because the heart and lungs are close to this point of contact, these are the organs injured most frequently. Although electric shock can paralyze the diaphragm or interrupt nerve impulses that regulate respiration (breathing), death usually results from electricity’s effect on the heart. The electrical charge breaks the normal rhythm of the heart and induces fibrillation ( a rapid, irregular fluttering) of the heart muscle, which prevents the organ from beating normally and pumping blood. 

Electric shock also can cause muscles to contract suddenly, which may propel a person to the ground or across a room. A strong electric shock that is not fatal usually interferes with the function of internal organs near the point of contact.

The sign and symptoms of electric shock include tingling, burns on the skin where the current entered or exited, muscle pain, headache, loss of consciousness, irregular breathing or lack of breathing, and cardiac arrest. 

In giving first aid to an electric-shock victim, a caregiver must not touch the victim with bare hands until the source of electricity has been removed safely or the power source shut off. If the victim is not breathing, mouth-to-mouth resuscitation is necessary. Burns should be rinsed or immersed in cold water, blotted dry, and kept clean and covered until the victim can be examined by a physician.

The common method of protecting against property damage through circuit overloads and over heating are fuses and circuit breakers. Every hot wire must be protected by a fuse or circuit breaker.

Personal safety in working with electricity involves common sense and a fundamental knowledge of electricity.

The main thing to remember is not to become part of a circuit yourself. As with other circuit  components,  the current drawn by a human body depends on its resistance and the voltage source

I   =     V / R

If the skin is dry there is usually a high resistance of 100000 ohms and an electric shock may only be an uncomfortable surprising tingle. However, if the skin is wet, especially with sweat which contains salts or water of good conducting ability, the resistance falls drastically to, perhaps, just a few hundred ohms that is low enough to allow injurious and fatal current flows.

A 60 W light bulb operating on 120 V draws 0.5 A or 500 mA of current. Death can result for  this current. The  table below gives the physiological effects of current passing through the human body.

Corrosion is the process of destruction or wearing away of materials caused by the chemical or electrochemical reaction of a metal or an alloy with non-metals in the surrounding environment.

When a metal corrodes it changes from a metal to a compound of a metal. This process is called oxidation. The compounds formed are oxides, sulphides, hydroxides and carbonates.

In dry conditions, oxidation occurs and the corrosion of the metal is due to chemical action only. Some examples are :

1. Aluminium exposed to air forms a very thin coating of oxide, Al2O3. Further corrosion is prevented unless the metal is exposed to acidic/alkaline surroundings.

2. Copper when exposed to water and carbon dioxide forms a light green coating called patina, which is protective when a certain thickness is formed.

3. Zinc under normal weather corrodes to a white coating of zinc carbonates, which is not sufficiently protective. Pitting corrosion occurs where small pits of localised corrosion become deeper and deeper.

In wet conditions, corrosion is both electrical and chemical i.e. 'electrolytic'. This involves an electric cell consisting of an anode, a cathode and an electrolyte (a conducting liquid). 

The anode corrodes or dissolves. The cathode does not corrode but may acquire a fresh coating of metal. A metal becomes an anode (higher in the series) or cathode depending on its position in the electro-chemical series 

Anodes and cathodes appear on steel because steel consists of two different compounds (the 'grains' can be seen under a microscope). In mild steel, the grains are called ferrite and pearlite, Fig. 3.

Ferrite is a nearly pure crystalline iron with a very small amount of carbon in it. Pearlite consists of alternate layers of ferrite and cementite. Cementite is a compound of iron and carbon - iron carbide, FeR3RC. Ferrite is known to be anodic to pearlite.

The economic importance of suitable protective measures is an inseparable part of the national bill of corrosion. A part of this might well be reduced if more attention were paid to protective measures at the earliest stages of project design. The extra expense in producing a well-protected structure is more than offset by the reduction in maintenance costs and preservation of the structure.

Passive corrosion protection involves covering the metal with some form of non-metallic or metallic coating. Non-metallic coatings are paint, bitumen, grease etc. An example of metallic coating is the alloying of steel with chromium to make the iron/steel passive i.e. not actively corrosive, due to layer of chromium oxide protecting the surface.

Types of metallic coatings

• Electrolysis (e.g. galvanic nickel plating)

• Dipping in molten metals (e.g. hot-dip zinc coating)

• Diffusion treatment (e.g. diffusion chromium plating)

• Spray metal coating (e.g. zinc coating by spraying)

Paints are generally consists of a medium, a pigment and solvents (e.g. white spirits/naphtha) and possibly a drying agent. Before paints are applied, some form of surface pre-treatment must be carried out. Dust, grease, oil, and loose bits of the material itself must be removed before the paint is applied.

Mechanical methods (e.g. wire brush), thermal methods (e.g. torch), and chemical techniques (e.g. acid treatment) can be used. Sand blasting is the most important method. An undercoat is necessary to cover surface roughness caused by sand blasting.

Coating failures can be very costly, leading to premature deterioration and failure. Many times blame is placed on the coating materials when, in fact, most failures occur in applications where specifications for surface preparation, undercoating or coating application have not been prepared or are just not followed. For example, improper or incomplete cleaning and removal of rust, mildew, abrasive or other surface contamination can lead to incomplete adhesion of the coating to the metal surface.

Additionally, inadequate curing between coats and improper mixing of multi- component systems tend to occur too often. However, several common types of coating failures can be categorised as indicated below, along with their causes and remedies:

Chalking

Chalking is the formation of a powdery material on the surface of the coating. This form of surface deterioration often results from inadequate resistance of the coating to ultraviolet (UV) light. The remedy is to utilize a topcoat with greater resistance to UV radiation.

Erosion

Erosion is the removal of the coating by contact with surrounding elements. This loss of coating material reduces the thickness. Reformulation or selection of alternative materials with higher hardness should reduce erosion effects.

Blistering

Blistering is the formation of small to large, broken or unbroken bubbles, under or within the coating. Most common blistering results from improper solvent oil or moisture contamination, and surface contamination with salts (osmotic blistering) or by excessive cathodic protection. To minimize blistering problems, greater attention is needed on surface preparation to remove contamination and enhance adhesion between the coating and the substrate.

Orange peeling

Formation of “hills and valleys” on the coated surface, resembling an orange peel. This problem typically results from excessively high viscosity during application or solvent evaporation rate. Changing coating conditions or solvent can eliminate orange peeling. Once formed, it can often be removed by sanding and applying another coat of material.

Pin holing

Occurrence of small holes that provide a path of exposure to the substrate, due to improper spray atomisation or segregation of the resin from the pigment in the coating. In thin film epoxy coatings, excessive heat can cause similar effects by foaming the resin. Its effects may be minimized after application and curing by application of additional coating under more optimum conditions.

Biofouling refers to the unwanted accumulation of marine organisms such as bacteria, algae, barnacles, and mussels on submerged surfaces, including ship hulls, pipelines, and reservoirs. This buildup of biological material can create significant operational and economic challenges.

1. Microorganisms & Biofilms – The first stage of biofouling begins with microscopic bacteria forming biofilms, which serve as an adhesive base for larger organisms.

2. Algal Growth – Algae attach to the biofilm and multiply, creating a rough surface that facilitates further accumulation.

3. Attachment of Larger Organisms – Over time, barnacles, mussels, and other marine life settle on the surface, increasing resistance to water flow.

• Increased Fuel Consumption – A fouled hull increases hydrodynamic drag, causing ships to consume more fuel.

• Structural Damage – Biofouling can corrode metal surfaces and damage coatings, leading to higher maintenance costs.

• Reduced Speed & Efficiency – Vessels with heavy fouling experience performance loss, requiring more power to maintain speed.

• Spread of Invasive Species – Ships transfer marine organisms to new environments, disrupting ecosystems.

Antifouling is the process of preventing or minimizing the accumulation of marine organisms on ship hulls and other submerged structures. It involves using special coatings, chemicals, or mechanical cleaning methods.

1. Antifouling Paints & Coatings

   • Biocidal Paints – Contain toxic substances (e.g., copper-based compounds) that deter organism growth.

   • Foul-Release Coatings – Silicone-based coatings that make it difficult for organisms to attach to the hull.

2. Ultrasonic Antifouling

   • Uses high-frequency sound waves to disrupt organism attachment on surfaces.

3. Electrochemical Methods

   • Generates low electric currents to deter marine life from settling on ship surfaces.

4. Regular Hull Cleaning

   • Manual or robotic cleaning systems to remove accumulated organisms before they become a problem.

5. Ballast Water Management

   • Reducing organism transfer by treating ballast water before discharge.

• International Maritime Organization (IMO) Antifouling Systems (AFS) Convention bans harmful substances (like tributyltin, TBT) in antifouling paints.

• Shipowners are required to use eco-friendly antifouling measures to comply with environmental standards.

Ballast water is the water taken in by ships to maintain stability, balance, and structural integrity during voyages. It is usually stored in ballast tanks and is taken in or discharged depending on cargo load, weather conditions, and ship stability requirements.

Ballasting: The process of taking in water when the ship is empty or partially loaded.

Deballasting: The process of discharging ballast water when the ship is fully loaded.

While essential for safe maritime operations, ballast water can cause environmental problems by introducing invasive species into new ecosystems.

Ballast water can carry invasive aquatic species such as bacteria, viruses, algae, and small marine animals from one region to another. When discharged into a new marine environment, these organisms can:

✅ Disrupt local ecosystems.
✅ Harm native marine life.
✅ Affect fisheries and aquaculture.
✅ Introduce harmful pathogens.

To prevent ecological damage, Ballast Water Management (BWM) practices are required under international regulations.

The International Maritime Organization (IMO) introduced the Ballast Water Management Convention (BWM Convention) to regulate how ships handle ballast water.

• Adopted: 2004

• Enforced: September 8, 2017

• Purpose: Reduce the transfer of harmful marine organisms by managing ballast water discharge.

• Requirement: Ships must treat ballast water to meet specific environmental standards.

Key IMO Ballast Water Regulations:

• All ships must implement a Ballast Water Management Plan (BWMP).

• Ships must have a Ballast Water Record Book for inspections.

• New ships must have Ballast Water Treatment Systems (BWTS) to filter and disinfect ballast water.

• Existing ships must retrofit treatment systems before the deadline set by IMO.

Other regulatory bodies include:

• U.S. Coast Guard (USCG) – Requires additional ballast water treatment standards.

• European Union (EU) Regulations – Enforce IMO rules with strict compliance checks.

To comply with regulations, ships must treat ballast water before discharge. There are three main treatment methods:

1. Physical Treatment

   • Filtration – Removes larger organisms and sediments before water enters ballast tanks.

   • Ultraviolet (UV) Radiation – Kills microorganisms using UV light.

2. Chemical Treatment

   • Chlorination & Chemical Biocides – Destroys harmful organisms in the ballast water.

   • Dechlorination – Ensures chemicals are neutralized before discharge.

3. Mechanical Treatment

   • Oxygen Deprivation – Removes oxygen from ballast tanks to kill organisms.

   • Heat Treatment – Uses heat to sterilize ballast water before release.

Each method must comply with IMO-approved treatment standards to prevent environmental damage.

To minimize environmental risks, ships should follow best practices for ballast water management:

✅ Minimize Ballast Uptake in Polluted Areas – Avoid taking ballast water near ports, sewage outflows, and shallow waters.
✅ Use Onboard Ballast Water Treatment Systems – Ensure compliance with IMO and national regulations.
✅ Maintain Ballast Water Record Keeping – Keep a detailed log of all ballast water intake and discharge activities.
✅ Regularly Inspect and Clean Ballast Tanks – Prevent sediment buildup that may harbor invasive species.
✅ Follow Port Authority Guidelines – Some ports have additional rules on ballast water discharge.

Despite technological advancements, ballast water management faces several challenges:

• High Cost of Treatment Systems – Retrofitting older ships with ballast water treatment systems is expensive.

• Operational Delays – Treatment processes may slow down cargo operations.

• Complex Regulations – Varying international and regional regulations make compliance difficult.

• Effectiveness of Treatment Methods – Some treatment technologies may not work effectively in all water conditions.

To address these challenges, ship operators must invest in proper training, equipment, and compliance strategies.

1. When a metal corrodes, it changes from a metal to a compound of a metal (corrosion product). Name four such corrosion products. Which of these corrosion products become protective coatings that prevent further corrosion?

2. State the three elements in an electrolytic (galvanic) corrosion. Which of these corrodes?

3. A steel ship is fitted with a bronze propeller. Which one, steel or bronze, will corrode? What can be done to reduce the corrosion?

4. Mild steel consists of ferrite and pearlite. Describe the corrosion of mild steel.

5. Give three arrangements of structural sections that can prevent water retention and hence reduce corrosion.

6. Name two methods of active corrosion control.

7. Sacrificial metals are often used as sacrificial anodes to protect metal works from corrosion. If you need to protect the underwater portion of a steel vessel, which two metals would you use as sacrificial anodes?

8. Describe the impressed current method of corrosion prevention.

9. State the basic composition of paint and the function of paint in corrosion prevention.

10. Name four metallic coatings often used in passive corrosion protection.

11. Name the methods of surface pre-treatments often used before organic coatings are applied. What do these surface treatments attempt to achieve?

12. State the causes and remedies for the following types of coating failure:

(a) Chalking (b) Erosion (c) Orange peeling (d) Pin-holing