Corrosion Chemistry: Introduction and Theories

The volume ratio of HCl to HNO3 used to prepare aqua regia is 3:1.

It takes 45 minutes to completely remove nitric acid from the solution.

Iron sulfate is added to precipitate gold from the solution, with a recommended amount of 4.2 g per gram of gold.

<p>Concentrated HCl is used to dissolve the gold deposits and ensure their cleanliness through boiling and re-washing.</p> Signup and view all the answers

<p>The gold deposit should be dried at a temperature of 100°C.</p> Signup and view all the answers

<p>CPR is calculated using the formula CPR = K.W / (ρ.A.t).</p> Signup and view all the answers

<p>K is 87.6 for mmpy and 534 for mpy.</p> Signup and view all the answers

<p>The weight loss in milligrams is 40000 mg.</p> Signup and view all the answers

<p>The area is 30000 cm².</p> Signup and view all the answers

<p>The density is used in the denominator of the CPR formula, affecting the corrosion rate.</p> Signup and view all the answers

<p>Corrosion is the gradual deterioration or loss of metal at its surface due to chemical or electrochemical reactions between the metal and its surrounding environment.</p> Signup and view all the answers

<p>100 inch² is equal to 645 cm².</p> Signup and view all the answers

<p>Time period represents how long the weight loss occurs and affects the corrosion rate.</p> Signup and view all the answers

<p>According to the electrochemical theory, corrosion is an electrochemical process involving oxidation at the anode and reduction at the cathode, similar to reactions in a galvanic cell.</p> Signup and view all the answers

<p>The anode is where oxidation occurs, leading to the release of electrons, while the cathode is where reduction occurs and does not undergo corrosion.</p> Signup and view all the answers

<p>The CPR value is 37.424 mpy.</p> Signup and view all the answers

<p>Water acts as an electrolyte that enables ion conduction, facilitating the electrochemical reactions necessary for corrosion.</p> Signup and view all the answers

<p>About 80-90% of metallic materials produced worldwide are disposed of by engineers.</p> Signup and view all the answers

<p>The overall cost of corrosion in India amounts to around 2 lakh crore annually.</p> Signup and view all the answers

<p>Sudden failures due to corrosion can lead to catastrophic consequences, including loss of human life, especially in critical infrastructures like nuclear reactors and bridges.</p> Signup and view all the answers

<p>Corrosion prevention and control measures, such as protective coatings and cathodic protection, could potentially save about 20-25% of the losses incurred due to corrosion.</p> Signup and view all the answers

<p>Burning e-waste releases pollutants such as lead, cadmium, mercury, chromium, and dioxins.</p> Signup and view all the answers

<p>E-waste can have devastating effects on wildlife through habitat destruction and the introduction of toxic substances into their ecosystems.</p> Signup and view all the answers

<p>Technology leads to resource depletion by consuming minerals and fossil fuels faster than they can be replenished, resulting in environmental degradation.</p> Signup and view all the answers

<p>Lead exposure can cause damage to central and peripheral nervous systems, blood systems, and kidney damage, particularly affecting children's brain development.</p> Signup and view all the answers

<p>Recycling is a method of e-waste disposal that helps recover valuable materials and reduce landfill waste.</p> Signup and view all the answers

<p>Incineration can release toxic pollutants such as dioxins and heavy metals into the air, posing health risks.</p> Signup and view all the answers

<p>Mercury exposure can lead to chronic damage to the brain and respiratory disorders due to bioaccumulation.</p> Signup and view all the answers

<p>Burning plastics in e-waste produces dioxins, which can cause reproductive and developmental problems.</p> Signup and view all the answers

<p>Zinc corrodes while iron is protected because zinc has a lower reduction potential than iron, leading to zinc undergoing oxidation.</p> Signup and view all the answers

<p>Differential aeration corrosion occurs when a metal is exposed to varying oxygen concentrations; the area with lower oxygen becomes anodic and undergoes corrosion.</p> Signup and view all the answers

<p>Water-line corrosion occurs in partially filled tanks, where the area below the water line has lower oxygen concentration and becomes anodic, leading to corrosion.</p> Signup and view all the answers

<p>The anodic reaction is Fe → Fe2+ + 2e- (oxidation), and the cathodic reaction is 1/2 O2 + 2H2O + 2e- → 4OH- (reduction).</p> Signup and view all the answers

<p>In pitting corrosion, lower oxygen concentration can lead to localized corrosion even on otherwise protected surfaces.</p> Signup and view all the answers

<p>Saltwater enhances differential aeration corrosion by facilitating ionic conductivity, which increases the corrosion current flow between anodic and cathodic areas.</p> Signup and view all the answers

<p>A metal placed in an oxygen-rich environment will experience enhanced cathodic protection, as the increased oxygen concentration helps form reduction products that stabilize the metal.</p> Signup and view all the answers

<p>Preventive measures against water-line corrosion include coating the interior of tanks, regular maintenance, and ensuring adequate ventilation to mitigate oxygen concentration differences.</p> Signup and view all the answers

<p>It reduces waste volume by about 90% and generates heat for energy.</p> Signup and view all the answers

<p>Recycling prevents toxic chemicals from contaminating air, soil, and water, and conserves natural resources.</p> Signup and view all the answers

<p>Metals such as lead, copper, aluminum, silver, gold, and platinum can be recovered.</p> Signup and view all the answers

<p>It creates jobs for professional recyclers and establishes a market for recycled materials.</p> Signup and view all the answers

<p>The initial step involves grinding the CPUs to a thickness of 1 mm.</p> Signup and view all the answers

<p>Leaching involves adding concentrated nitric acid for a duration of 1 hour to dissolve metals.</p> Signup and view all the answers

<p>Separation and purification methods include solvent extraction and ion exchange.</p> Signup and view all the answers

<p>E-waste contains toxic chemicals that can harm the environment and human health if disposed of in landfills.</p> Signup and view all the answers