Protective Coatings Overview
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Questions and Answers

What is the main purpose of reverse osmosis in water treatment?

  • To reduce the pressure of water entering the system
  • To increase the turbidity of water
  • To remove dissolved solids from water (correct)
  • To increase the temperature of seawater
  • Which condition must be met regarding water turbidity before treatment can be effective in high pressure boilers?

  • Turbidity has no effect on treatment
  • Turbidity must be below 10 ppm (correct)
  • Turbidity must be above 10 ppm
  • Turbidity must be at least 5 ppm
  • What phenomenon allows solvent to flow from lower concentration to higher concentration in reverse osmosis?

  • Hydrostatic pressure application
  • Thermal expansion
  • Osmotic pressure (correct)
  • Diffusion
  • What is one of the disadvantages of using treatment equipment for high pressure boilers?

    <p>Requires expensive equipment and chemicals</p> Signup and view all the answers

    What is the primary source of chemical fuels in nature?

    <p>Crude oil, natural gas, and coal</p> Signup and view all the answers

    What is the gross calorific value (GCV) of the fuel in the given calculation?

    <p>12,638 cal/g</p> Signup and view all the answers

    How does the presence of hydrogen in fuel affect its net calorific value (NCV)?

    <p>Reduces the NCV due to heat losses during steam formation</p> Signup and view all the answers

    What correction is made for heat liberated during sparking in the calorimeter experiment?

    <p>Fuse wire correction</p> Signup and view all the answers

    What is the role of the acid correction in calorific value calculations?

    <p>To adjust for heat released during the formation of acids</p> Signup and view all the answers

    What factor is considered in calculating the cooling correction in a calorimeter experiment?

    <p>Rate of cooling</p> Signup and view all the answers

    What percentage of hydrogen is present in the fuel sample used in the first calculation?

    <p>0.7%</p> Signup and view all the answers

    When calculating the calorific value, what must be adjusted for due to the weight of the calorimeter?

    <p>The water equivalent of the calorimeter</p> Signup and view all the answers

    What is the latent heat of steam used in the calculations?

    <p>587 cal/g</p> Signup and view all the answers

    What is the main purpose of protective coatings on metals?

    <p>To provide a physical barrier against corrosion</p> Signup and view all the answers

    Which of the following is an example of an anodic coating?

    <p>Zinc on iron</p> Signup and view all the answers

    Which method is NOT a technique for applying metallic coatings?

    <p>Sputtering</p> Signup and view all the answers

    What happens when an anodic coating breaks?

    <p>A galvanic couple is formed causing accelerated corrosion</p> Signup and view all the answers

    What is the main characteristic of cathodic coatings?

    <p>They are produced using metals that are more cathodic</p> Signup and view all the answers

    In the process of galvanization, which substance is iron dipped into?

    <p>Molten zinc</p> Signup and view all the answers

    Which of the following statements is true about electroplating?

    <p>It uses an electrolytic solution</p> Signup and view all the answers

    What is a common practice to prevent corrosion in cathodic coatings?

    <p>Regularly checking and re-plating the coating</p> Signup and view all the answers

    What type of functional groups do cation-exchange resins primarily contain for exchanging H+ ions?

    <p>-COOH and -SO3H</p> Signup and view all the answers

    Which of the following statements best describes the regeneration of exhausted anion-exchange resins?

    <p>Exhausted anion resins are regenerated using strong bases.</p> Signup and view all the answers

    What sequence is recommended for treating hard water to prevent precipitation of hydroxides?

    <p>Pass through cation exchanger first and then anion exchanger.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of cation-exchange resins?

    <p>They should contain basic functional groups.</p> Signup and view all the answers

    What is one significant advantage of the ion-exchange process for water treatment?

    <p>It can be used on both highly acidic and highly alkaline water.</p> Signup and view all the answers

    During the anion-exchange process, what ion is typically replaced?

    <p>Cl-</p> Signup and view all the answers

    What is the main structure of ion-exchange resins?

    <p>Cross-linked long chain polymers with a microporous structure</p> Signup and view all the answers

    What happens to H+ ions during the cation exchange process in water treatment?

    <p>They are removed from the solution and replaced by cations.</p> Signup and view all the answers

    What is the primary role of the argon ions in the sputtering process?

    <p>To knock target atoms off</p> Signup and view all the answers

    Which type of sputtering is used for non-conductive materials?

    <p>Radio-frequency sputtering</p> Signup and view all the answers

    What is a key advantage of using sputter deposition over thermal evaporation?

    <p>Ability to deposit materials with high melting points</p> Signup and view all the answers

    What is formed when target atoms are knocked off during sputtering?

    <p>Thin film on the substrate</p> Signup and view all the answers

    What is the primary component of the gas used to create plasma in sputtering?

    <p>Argon</p> Signup and view all the answers

    In the sputtering process, what happens to the target atoms after being sputtered?

    <p>They are transported to the substrate to form a coating</p> Signup and view all the answers

    Which application is NOT typically associated with the sputtering method?

    <p>Plastic manufacturing processes</p> Signup and view all the answers

    What characterizes the plasma state in which argon is used during sputtering?

    <p>A state where particles are ionized</p> Signup and view all the answers

    Study Notes

    Protective Coatings

    • Protective coatings act as a barrier between metal and the environment.
    • They provide both corrosion protection and decorative value.
    • Coatings are classified as inorganic or organic.
      • Inorganic coatings: metallic and chemical conversion coatings
      • Organic coatings: paints, varnishes, enamels, lacquers

    Metallic Coatings

    • Anodic coatings:
      • Applied to cathodic metals using more anodic metals.
      • Examples: Zinc, Aluminum, Cadmium coatings on iron.
      • If the coating breaks, a galvanic couple forms and corrosion is enhanced.
      • The anodic coating sacrifices itself to protect the base metal.
      • The anodic coating is also called galvanization.
    • Cathodic coatings:
      • Applied to anodic metals using more cathodic metals.
      • Examples: Tin, Chromium, Nickel coatings on iron.
      • If a discontinuity forms, galvanic couple formation results in corrosion of the base metal.
      • To prevent corrosion, frequent inspection and re-plating is required.

    Methods of Metallic Coatings

    • Hot dipping: Dipping the base metal in a molten metal
      • Galvanizing: Dipping iron in molten zinc.
      • Tinning: Dipping iron in molten tin.
    • Metal cladding: Cladding the base metal with another metal.
    • Electroplating: Coating the base metal by passing direct current through an electrolytic solution containing the coating metal's soluble salt.
    • Electroless plating: Chemical plating, a coating process that uses a chemical reaction to deposit a coating without using an external electrical current.
    • Physical Vapor Deposition (PVD): Thin film deposition of metals or compounds using a vacuum-based process.
      • Sputtering: A PVD technique involving bombarding a target material with ions, leading to the ejection of atoms that deposit onto a substrate.
        • Application of sputtering: VLSI fabrication, thin film coatings, and deposition of materials with high melting points.
    • Chemical Vapor Deposition (CVD): A thin film deposition technique using chemical reactions on a substrate.

    PVD: Sputtering Method

    • Plasma: A state of matter similar to gas with a portion of ionized particles.
    • Process: A vacuum chamber is filled with argon gas, high voltage is applied causing ionization of argon to plasma, argon ions bombard the target material and the sputtered atoms are deposited onto the substrate.
    • Advantages: Strong film adhesion, good film density and high deposition rates.
    • Applications: VLSI fabrication, thin film coatings in diverse industries.

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    Description

    Explore the essential concepts of protective coatings in this quiz. Learn about the distinctions between inorganic and organic coatings, as well as the principles of anodic and cathodic coatings used for corrosion protection. Test your knowledge on how these coatings act as barriers and their decorative values in various applications.

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