Surface tension is caused by intermolecular forces that cause liquid molecules to stick together. This gives the surface of the liquid elastic properties. Surface tension allows water bugs to walk on water by distributing their weight to depress the surface without breaking through. It causes water to form spherical drops and objects like needles to float. Higher surface tension at lower temperatures causes folds in milk fat layers. Surface tension decreases with increasing temperature as intermolecular forces weaken. It can be calculated using the formula that divides the dragging force by the length of the surface or the work done divided by the change in surface area.
This document discusses different forms of corrosion. It classifies corrosion as wet/aqueous corrosion, which occurs in the presence of water, or dry/gaseous corrosion, which occurs at high temperatures. Wet corrosion is further broken down into uniform corrosion, galvanic corrosion, crevice corrosion, pitting, dealloying, intergranular corrosion, and others. Examples are provided for each type. The document also discusses high temperature corrosion processes like oxidation and corrosion in sulfur environments.
This ppt explains basics of corrosion, its significance, Mechanism of electrochemical and chemical corrosion, Cathodic protection, Anodic protection, Sacrificial protection, Galvanization, Concentration Corrosion, Pitting Corrosion and also describe about the prevention and control of corrosion with respect to protective coatings and modification in design.
Surface tension results from the greater attraction of liquid molecules to each other than to air molecules. This causes liquids to behave as if their surface is covered by a stretched elastic membrane, minimizing surface area. Water has a high surface tension due to hydrogen bonding between molecules. Surface tension is responsible for phenomena like water beading on leaves and insects floating on water. It is measured as a force per unit length and allows calculation of pressure differences across curved surfaces using the Young-Laplace equation.
The document discusses corrosion, which is defined as the degradation of a metal through a chemical reaction on its surface caused by its surrounding chemicals. It then discusses the chemical theory of corrosion, noting that oxygen and other gases can cause corrosion by directly reacting with metals. There are two main types of corrosion - dry corrosion, which occurs without moisture, and wet/electrochemical corrosion, which occurs when a metal is in contact with a conducting liquid. The document goes on to describe examples of different corrosion processes and methods used to protect metals from corrosion, including cathodic protection and coatings like paint.
Erosion corrosion occurs when the rate of material deterioration increases due to the combined effects of corrosion and mechanical wear from fluid flow. It can occur in pipes, valves, pumps and other equipment exposed to flowing liquids or gases. The mechanism involves turbulent flow damaging protective surface films and exposing the bare metal to chemical attack. Common signs are grooves, holes and valleys in the direction of flow. Prevention methods include design modifications to reduce turbulence, removing abrasive particles from the fluid, protective coatings, cathodic protection, and using more corrosion resistant materials.
Surface tension is caused by intermolecular forces that cause liquid molecules to stick together. This gives the surface of the liquid elastic properties. Surface tension allows water bugs to walk on water by distributing their weight to depress the surface without breaking through. It causes water to form spherical drops and objects like needles to float. Higher surface tension at lower temperatures causes folds in milk fat layers. Surface tension decreases with increasing temperature as intermolecular forces weaken. It can be calculated using the formula that divides the dragging force by the length of the surface or the work done divided by the change in surface area.
This document discusses different forms of corrosion. It classifies corrosion as wet/aqueous corrosion, which occurs in the presence of water, or dry/gaseous corrosion, which occurs at high temperatures. Wet corrosion is further broken down into uniform corrosion, galvanic corrosion, crevice corrosion, pitting, dealloying, intergranular corrosion, and others. Examples are provided for each type. The document also discusses high temperature corrosion processes like oxidation and corrosion in sulfur environments.
This ppt explains basics of corrosion, its significance, Mechanism of electrochemical and chemical corrosion, Cathodic protection, Anodic protection, Sacrificial protection, Galvanization, Concentration Corrosion, Pitting Corrosion and also describe about the prevention and control of corrosion with respect to protective coatings and modification in design.
Surface tension results from the greater attraction of liquid molecules to each other than to air molecules. This causes liquids to behave as if their surface is covered by a stretched elastic membrane, minimizing surface area. Water has a high surface tension due to hydrogen bonding between molecules. Surface tension is responsible for phenomena like water beading on leaves and insects floating on water. It is measured as a force per unit length and allows calculation of pressure differences across curved surfaces using the Young-Laplace equation.
The document discusses corrosion, which is defined as the degradation of a metal through a chemical reaction on its surface caused by its surrounding chemicals. It then discusses the chemical theory of corrosion, noting that oxygen and other gases can cause corrosion by directly reacting with metals. There are two main types of corrosion - dry corrosion, which occurs without moisture, and wet/electrochemical corrosion, which occurs when a metal is in contact with a conducting liquid. The document goes on to describe examples of different corrosion processes and methods used to protect metals from corrosion, including cathodic protection and coatings like paint.
Erosion corrosion occurs when the rate of material deterioration increases due to the combined effects of corrosion and mechanical wear from fluid flow. It can occur in pipes, valves, pumps and other equipment exposed to flowing liquids or gases. The mechanism involves turbulent flow damaging protective surface films and exposing the bare metal to chemical attack. Common signs are grooves, holes and valleys in the direction of flow. Prevention methods include design modifications to reduce turbulence, removing abrasive particles from the fluid, protective coatings, cathodic protection, and using more corrosion resistant materials.