Midterm 1st Topic Flashcards
when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the material
Corrosion
the process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration
Diffusion
– the measure of hotness or coldness expressed in terms of any of several scales, including Fahrenheit and Celsius
– indicates the direction in which heat energy will spontaneously flow—i.e., from a hotter body (one at a higher temperature) to a colder body (one at a lower temperature)
Temperature
– a measure of the ability of water to pass an electrical current
– the measure of the ease at which an electric charge or heat can pass through a material
Conductivity
a material which gives very little resistance to the flow of an electric current or thermal energy
Conductor
a chemical substance, usually a liquid, which contains hydrogen and can react with other substances to form salts
Acid
occurs when two dissimilar metals are present in an electrolytic medium
Electrochemical Corrosion
– a chemical compound that dissociates into ions and hence is capable of transporting electric charge - i.e.
– an electric conductor; unlike metals the flow of charge is not a flow of electrons, but is a movement
Electrolyte
Main Factors influencing the Rate of Corrosion
● Diffusion
● Temperature
● Conductivity
● ph (Acid)
● Electrochemical Corrosion/Corrosion Potential
● Types of Ions/Ions
electrically charged atoms
Ions
Two types of ions
Cations & Anions
positively charged ions
Cations
negatively charged ions
Anions
when metals collect this, an electrochemical reaction causes the steel to corrode
Moisture
– also known as metal oxides
– forms when oxygen reacts with metal atoms
Rust
– a coating which is the major line of defense against corrosion in ballast tanks and void spaces
– in ballast tanks, they are commonly used and there is some interest in using inert gas atmospheres
Hard Epoxy Coating
– a means of preventing electrochemical wastage is required
– a system of preventing corrosion by forcing all surfaces of a structure (e.g. hull) to be cathodes by providing external anodes
Cathodic Protection
Types of Cathodic Protection
Sacrificial Anode System/Sacrificial Anodes
Impressed Current System/Impressed Current Cathodic Protection (ICCP)
Type of Cathodic Protection that can be accomplished by fitting aluminium, magnesium or zinc anodes in tanks or underwater portion of a ship, which waste away by galvanic action
Sacrificial Anode Cathodic Protection
Type of Cathodic Protection that can be achieved by superimposing on the hull an impressed current provided by a remote power source through a small number of inert anodes
Impressed Current Cathodic Protection
– metals or alloys attached to the hull that have a more anodic, i.e. less noble, potential than steel when immersed in sea water
– supply the cathodic protection current, but will be consumed in doing so and therefore require replacement for the protection to be maintained
Sacrificial Anodes
– may be safely employed
– sacrificial anodes made of zinc that are attached to a ship’s hull
– a critical component of a cathodic protection system, which is used to protect the ship’s metal structure from corrosion
– they work by corroding instead of the hull, providing protection against corrosion
Zinc Anodes
– consists of a number of anodes (lead or platinised titanium) fitted to the hull at
selected places below the waterline, and control equipment which automatically
regulates the anode current to the required value
– consists of anodes connected to a DC power source
Impressed Current Cathodic Protection (ICCP)
an electrical device used to convert alternating current (AC) into direct current (DC) by allowing a current to flow through the device in one direction only
Rectifier
Process of converting alternating current (AC) into direct current (DC)
Rectification
the negative or reducing electrode that releases electrons to the external circuit and oxidizes (corrode) during and electrochemical reaction
Anode
the positive or oxidizing electrode that acquires electrons from the external circuit and is reduced during the electrochemical reaction
Cathode
combined with inappropriate manipulations may lead to damage of a vessel, threatening the cargo, the environment or, even worst, human life
Heavy Weather
Preventive Actions to be taken for Heavy Weather
- Always the cargo to be loaded as per Cargo Security Manual
- Speed of the vessel need to be adjusted with the course and slow down if needed
- Consideration of the actual stability conditions
- Maintaining of the lashing equipment to be in a good condition (container ships or Ro-Ro vessels)
- Hatch covers and seals must be in good water-tight condition (bulk carriers)
- Officers to be aware and well trained to handle the mentioned risks
- Alternate route through a less risky course
– the manual required on all types of ships engaged in the carriage of all cargoes other than solid and liquid bulk cargoes
– cargo units, including containers, shall be loaded, stowed and secured throughout the voyage in accordance with it approved by the Administration
Cargo Securing Manual
Preventing Structural Damage of the Ship
- The selection of high-quality materials and effective coating systems is pivotal in preventing hull damage
- Investing in robust and corrosion-resistant materials during construction or repair can enhance the vessel’s longevity and reduce the likelihood of structural weaknesses
Precautions while cargo loading operations
Pre-arrival checks
Ship-Shore Safety Checklist
must be carried out before reaching the loading port on the cargo/bunkering systems and equipment
Pre-arrival checks
must be agreed with the terminal and understood by all personnel involved in the cargo operations
Ship-Shore Safety Checklist
– everywhere, incur a measure of liability for the safety of the goods
– in common-law countries, liable for any damage or for the loss of the goods that are in their possession as carriers, unless they prove that the damage or loss is attributable to certain excepted causes
Carriers
