Corrosion and Fluid Mechanics Quiz

The removal of dissolved oxygen from boiler feedwater using a chemical reducing agent like sodium sulfite.

The process of removing suspended solids from water by allowing them to settle at the bottom.

The pH of boiler feedwater should be slightly alkaline (above 7) to prevent corrosion.

A cell that converts electrical energy into chemical energy.

The tendency of a metal to corrode in a specific environment, measured as a voltage difference between the metal and a standard electrode.

The process of corrosion where metal surfaces are attacked by acids or acidic vapors.

The measure of a fuel's heating capacity, taking into account the heat released by the combustion of both combustible and non-combustible components.

Inorganic compounds present in fuel that form ash after combustion.

A fuel is a substance that can be burned to release energy. It mainly consists of carbon and hydrogen, which easily react with oxygen in the air to produce heat and light.

Sacrificial Anode is a more active metal connected to the metal to be protected, which corrodes instead of the protected metal.

Surface tension is the ability of a liquid to resist an external force, like a drop of water forming a sphere. For efficient fuel combustion, a lower surface tension is essential for proper atomization, allowing the fuel to mix better with air.

The Sacrificial Anode must be more anodic (more prone to corrosion) than the metal it's protecting.

Dissolved oxygen in boiler feed water can cause corrosion. Reducing agents react with oxygen, removing it from the water.

Silver acts as the Cathode in electroplating iron. It's the surface where the silver ions are reduced to form a protective layer.

Cation exchange resins are used to remove positively charged ions (cations) like calcium and magnesium from water. They are used in water softening processes.

The cathodic reaction in Differential Aeration Corrosion involves oxygen and water, producing hydroxide ions (OH-) at the cathode.

Successful coating protection relies on a good barrier, a clean surface, and the formation of an inactive layer.

Alum is a chemical commonly used in water treatment to remove suspended colloids and oil. It acts as a coagulant, causing tiny particles to clump together for easier removal.

Metallic copper reacts with ammonia to form a compound that causes corrosion. The ammonia molecules attack the copper atoms, weakening the structure.

Intergranular corrosion occurs due to a potential difference between grain boundaries and the bulk metal caused by precipitation of impurities at the grain boundaries.

An inert barrier prevents corrosion by isolating the metal from the corrosive environment.

Galvanic corrosion happens when two dissimilar metals are connected in an electrolyte. The metal with a lower potential (more reactive) corrodes faster. This is why different electrolytes (like seawater) can create different corrosion rates.

Stress corrosion cracking occurs when a material is under stress and exposed to a specific corrosive environment. The combination of stress and the corrosive agent weakens the material, leading to cracking.

Impressed current method requires a power source to drive the cathodic protection current.

Cathodic protection is used to protect pipelines carrying corrosive substances like crude oil. This method involves introducing an electric current to create a protective layer on the pipe's metal surface, preventing corrosion.

Inhibitors are chemicals added to the corrosive environment to slow down or prevent metal corrosion. They work by creating a protective film, reacting with corrosive agents, or altering the corrosion process.

Impressed current cathodic protection involves using an external power source to create a protective current flow. The system ensures that the metal surface being protected is at a more negative potential than the surrounding environment, thus preventing corrosion.

The placement of anodes around a structure to protect it from corrosion is considered incorrect protection. This method is inefficient because it does not provide uniform protection across the entire surface.

Corrosion inside boilers can be caused by chloride salts, acidity, dissolved oxygen, and bacteria. These factors create conditions that accelerate the degradation of the boiler's metal components.

Scale formation in boilers is primarily due to dissolved salts in cold water, which form a dry adhesive layer. This layer can impede heat transfer and lead to overheating.

Permanent hardness in water is caused by the presence of calcium and magnesium salts, particularly sulfates. These salts cannot be easily removed by boiling and can cause scaling and other problems.

Decreasing the specific gravity of a fuel usually means an increase in the percentage of paraffin in the fuel. This leads to improved ignition characteristics.

Good combustion requires high hydrogen content in the fuel and lower specific gravity and surface tension. These factors contribute to a more efficient and complete burning process.

The pH of water entering an anion exchange resin should be less than 7. Anion exchange resins remove negatively charged ions, and water with a pH less than 7 indicates the presence of acidic components that need to be removed.

The feeding water for boilers should be deionized and free from dissolved oxygen. Deionized water minimizes the formation of scale and corrosion, while the absence of oxygen prevents oxidation and deterioration.

The flash point of a fuel refers to the lowest temperature at which the fuel will ignite when exposed to a source of ignition. It's not directly related to density or evaporation but is a significant safety parameter.

Lowering the calorific value of a fuel can be caused by factors like the composition of the fuel, water formation, and the presence of hydrogen (which is a less energy-dense component).

Sludge that forms inside water pipes is a result of impurities in the water. These impurities can accumulate and form deposits that hinder water flow and affect the pipes' efficiency.

Refers to the impurities present in the fuel. These impurities can be inorganic substances like ash or mineral content.

Increasing the percentage of paraffins in the fuel leads to better ignition properties.

The greater the amount of hydrogen in a fuel, the higher its calorific value, meaning it produces more energy when burned.

The dynamic viscosity of a fluid is related to the cohesive forces between the fluid molecules.

Kinematic viscosity is influenced by factors like the nature of the surface (smooth or rough), the adhesive forces, and the motion of the fluid.

A decrease in the hydrogen content of a fuel leads to a decrease in its calorific value, meaning it produces less energy.

The formation of carbon monoxide during fuel combustion occurs due to incomplete combustion caused by a lack of sufficient air.

The specific gravity of a fuel tends to decrease as the percentage of paraffins increases because paraffins are less dense than other hydrocarbons.