Galvanic Series and Metal Corrosion
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Questions and Answers

Which factor is negatively associated with the rate of corrosion?

  • Higher impurity levels
  • Increased temperature
  • Greater specific volume ratio (correct)
  • Smaller anodic area

    • The purity of a metal has no effect on its tendency to corrode.

    False

    What is the relationship between humidity and the rate of corrosion?

    Higher humidity increases the rate of corrosion.

    Corrosive products that are ______ in nature promote continuous corrosion as they expose the underlying metal surface.

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

    Match the following factors with their effect on corrosion:

    <p>Temperature = Increased corrosion rate Acidic media = More corrosive than neutral Impurities in atmosphere = Increases corrosion risk Physical state of metal = Smaller grain size leads to greater corrosion</p> Signup and view all the answers

    What happens to a metal with smaller grain size in terms of corrosion?

    <p>It shows greater corrosion.</p> Signup and view all the answers

    A pure metal is more likely to corrode than an alloy.

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

    How does the presence of suspended particles in the atmosphere influence corrosion?

    <p>They absorb moisture and act as strong electrolytes, enhancing corrosion.</p> Signup and view all the answers

    What is the preferred characteristic of the metal selected to minimize corrosion?

    <p>Noble metals</p> Signup and view all the answers

    Using metals that are far apart in the electrochemical series can help reduce corrosion.

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

    What should be avoided in the design of structures to minimize impurities related to corrosion?

    <p>Sharp corners and recesses</p> Signup and view all the answers

    An anodic portion will suffer __________ due to the process of corrosion.

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

    Which method is recommended to connect dissimilar metals to prevent corrosion?

    <p>Insulating fitting</p> Signup and view all the answers

    Match the following design elements to their effectiveness in preventing corrosion:

    <p>Poor design = Bolt joints Better design = Smooth bends Best design = Weld joints</p> Signup and view all the answers

    Preventing the creation of stagnant pools or damp areas is crucial for corrosion control.

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

    What is one method to improve the connection of dissimilar metals?

    <p>Use an insulating fitting</p> Signup and view all the answers

    Which method of cathodic protection uses a more anodic metal to protect the metallic structure?

    <p>Sacrificial anodic protection</p> Signup and view all the answers

    Impressed current cathodic protection involves using an external source to neutralize the corrosion current.

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

    What is the purpose of a sacrificial anode in cathodic protection?

    <p>To corrode instead of the protected metallic structure.</p> Signup and view all the answers

    In the galvanizing process, a layer of _____ is applied to iron or steel.

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

    Match the following coating methods with their descriptions:

    <p>Hot dipping = Coating with a low melting metal Galvanizing = Coating with zinc on iron or steel Tinning = Coating of tin on iron Surface coatings = Applying a protective layer onto the surface</p> Signup and view all the answers

    Which of the following constituents of paint is responsible for providing color?

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

    The vehicle in paint refers to the solid component that gives color to the paint.

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

    Anodic coatings involve coating a base metal with a more _____ metal.

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

    What is the primary purpose of metal cladding?

    <p>Protect the base metal from corrosion.</p> Signup and view all the answers

    Electroplating involves coating a noble metal over a more reactive metal.

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

    What is another name for electroless plating?

    <p>Immersion plating or displacement plating</p> Signup and view all the answers

    Organic coatings, such as ______ and lacquers, protect metal surfaces from corrosion.

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

    Which of the following methods involves using a more active metal to protect iron from corrosion?

    <p>Sacrificial Anode Protection</p> Signup and view all the answers

    Match the method of corrosion protection with its description:

    <p>Sacrificial Anode Protection = More active metal prevents corrosion of iron Impressed Current Cathodic Protection = External current neutralizes corrosion current Anodic Coatings = Coated with more active metals Cathodic Coatings = Coated with more noble metals</p> Signup and view all the answers

    Organic coatings are exclusively used for decorative purposes and have no protective function.

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

    In anodic coatings, metal is coated with a more _____ metal.

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

    Study Notes

    Galvanic Series

    • A table showing the order of reactivity of metals (or alloys) in a corrosive environment, from most active (anodic) to least active (cathodic).
    • More active metals corrode preferentially when in contact with less active metals.
    • Examples include magnesium (most active) and platinum (least active).
    • The galvanic series helps predict which metal will corrode more quickly in a given environment.

    Nature of the Metal

    • Physical state: Corrosion rate depends on the size of the metal's grains; smaller grains lead to higher corrosion rates.
    • Purity: Impurities in a metal create localized electrochemical cells leading to more rapid corrosion. Pure metals are less prone to corrode.
    • Overvoltage: The amount of voltage required to initiate a reaction. Lower overvoltage increases corrosion rate.
    • Surface film: A thin oxide layer forms on most metals. A higher volume ratio of oxide-to-metal indicates slower oxidation corrosion rates.
    • Relative areas of anodic and cathodic parts: If the anodic area is very small compared to the cathodic area, corrosion is accelerated.
    • Position in the galvanic series: The greater the difference in positions within the series, the faster the corrosion of the anodic substance.
    • Passive character of metal: Certain metals display a passive character, where a thin, protective oxide layer forms, thus slowing or stopping corrosion.
    • Solubility of corrosion products: If corrosion products are soluble, corrosion will be faster. If they are insoluble, a barrier is created reducing further corrosion.
    • Volatility of corrosion products: If corrosion products are volatile, corrosion will be more rapid.

    Nature of the Corrosive Environment

    • Temperature: Higher temperatures increase corrosion rates due to increased ion diffusion.
    • Humidity: Higher humidity increases corrosion rates by providing more moisture, acting as solvent for corrosive gases.
    • Impurities in the atmosphere: Corrosive gases like CO2, H2S, SO2, and acid fumes increase the acidity and conductivity of the environment, accelerating corrosion.
    • Suspended particles: Chemically active particles like NaCl increase the corrosive nature. Chemically inactive particles (e.g., charcoal) increase corrosion by trapping moisture and gases.
    • pH: Acidic environments are more corrosive than neutral or alkaline environments.
    • Concentration of oxygen: Differential oxygen concentration leads to concentration cells, accelerating corrosion. Higher oxygen concentration leads to faster corrosion
    • Conductance of medium: Higher ion content increases corrosion.
    • Flow velocity: High flow velocities may reduce corrosion, but very high flow or turbulent flow can accelerate it.

    Protection from Corrosion (Preventive Measures)

    • Material Selection: Choosing corrosion-resistant materials or using materials with similar electrochemical properties.
    • Proper Designing: Avoid sharp corners and recesses, use smooth bends to prevent accumulation of impurities, avoid dissimilar metals, if inescapable, space them to minimize contact in corrosive environment, create larger anodic surface against cathodic.
    • Corrosion Control: Employing methods to protect metals from corrosion. Examples include material selection, coatings (hot dipping, electroplating, etc.) and cathodic protection.
    • Cathodic Protection: A method to prevent corrosion by forcing the metal to be protected to behave like a cathode, (by connecting to a more anodic metal or by using an impressed current).

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    Related Documents

    Corrosion Notes - Applied Chemistry PDF

    Description

    This quiz explores the Galvanic Series and its implications on metal reactivity in corrosive environments. It covers concepts such as the physical state of metals, purity, overvoltage, and surface films that influence corrosion rates. Test your understanding of how different metals behave in relation to one another in terms of corrosion.

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