Gases and Corrosion in Automotive Engineering

• The document pertains to gases and corrosion, aimed at students in their first year, semester 1, CE No: 1.3, with 10 lessons.
• The focus is on equipping students with knowledge about the use of various gases, their potential risks, and effects, particularly regarding corrosion, in the automotive industry.

Learning Objectives

• To have a review of the states of matter and their changes.
• To learn about different gases used in automobiles and their associated risks.
• To understand how gases affect materials, focusing on corrosion and methods to protect against it.

Situation Resolution Directives

• Answer open-ended questions precisely using professional terminology.
• Fill in missing information in texts with appropriate terms.
• Mark true or false statements with an (X) in the corresponding column.
• Select the correct option or assign the appropriate letter; one answer per question is correct without special instructions.
• Show calculation steps clearly, including the process and units.

CE Objectives

• Students should be able to list the three states of matter (solid, liquid, gas) and the transitions between them.
• Students should know the most important properties and applications of oxygen, nitrogen, and argon.
• Students should describe the formation and structure of carbon compounds like carbon monoxide and carbon dioxide.
• Students should be able to name the main characteristics and applications of carbon monoxide, carbon dioxide, and acetylene.
• Students should be able to identify reasons for corrosion protection in auto body repairs.
• Students should explain the concepts of corrosion and resistance to corrosion.
• Students should explain the electrochemical principle of metals.
• Students should describe and differentiate between various types of corrosion.

States of Matter

• Matter exists in three states: solid, liquid, and gas.
• Physical transformation involves the state of matter remaining the same, while chemical transformation involves a change in the matter itself.
• Examples of physical transformation include temperature and stretching, where the chemical species do not change but interactions between molecules or atoms do.
• Examples of chemical transformation include decomposition of fruit (Mentos, coca) or rusting of iron, involving a chemical product.
• Transitions between states:
  • Solid to Liquid: Fusion
  • Liquid to Solid: Solidification
  • Liquid to Gas: Vaporization
  • Gas to Liquid: Condensation
  • Solid to Gas: Sublimation
  • Gas to Solid: Sublimation inverse

Properties and Applications of Gases

• Oxygen:
  • Vaporization Temperature: -183°C
  • Solidification Temperature: -219°C
  • Natural: Yes
  • Dangerous: No
  • Chemical Symbol: O
  • Applications: Oxyacetylene welding, respirator masks
• Nitrogen:
  • Vaporization Temperature: -195.8°C
  • Solidification Temperature: -210°C
  • Natural: Yes
  • Dangerous: No
  • Chemical Symbol: N
  • Applications: Fabrication of ampoules, tire inflation
• Argon:
  • Vaporization Temperature: -185.8°C
  • Solidification Temperature: -189°C
  • Natural: Yes
  • Dangerous: No
  • Chemical Symbol: Ar
  • Applications: TIG-MIG welding, double glazing insulation

Carbon Compounds

• Carbon Monoxide (CO):
  • Chemical formula: CO
• Carbon Dioxide (CO2):
  • Chemical formula: CO2

Characteristics of Gases

• Carbon Dioxide:
  • Vaporization Temperature: -56.6°C
  • Solidification Temperature: -78.48°C
  • Natural: Yes
  • Dangerous: No
  • Symbol: CO2
• Carbon Monoxide:
  • Vaporization Temperature: -191°C
  • Solidification Temperature: -205°C
  • Natural: Yes
  • Dangerous: Yes
  • Symbol: CO
• Acetylene:
  • Vaporization Temperature: -84.7°C
  • Solidification Temperature: -80.7°C
  • Natural: No
  • Dangerous: No
  • Symbol: C2H2

Applications of Carbon Dioxide

• Gaseous: Fire extinguishing, component giving sparkle in drinks, component needed for photosynthesis
• Liquid: Refrigerant for freezing foods and for the electronic industry, extinguishing agent in carbon dioxide extinguishers
• Solid: Dry ice for cleaning, snow for cooling, dry ice for degassing

Acetylene (C2H2)

• It is exceedingly flammable and can decompose spontaneously in an explosive manner.
• Applications include flames for acetylene lamps, combustible for welding, and in the production of PVC (plastic).

Rust and Corrosion

• Rust is a reddish-brown substance formed when iron-containing compounds corrode in the presence of oxygen and water.
• Risks of a rusted vehicle in an accident include increased deformation and injury due to reduced resistance.
• Mechanical methods to remove rust: Sandblasting, grinding, sanding, scraping, and brushing.
• Chemical methods to remove rust: De-rusting using phosphoric acid, electrolysis and with rust converters.
• Precautions for chemical methods: Use a mask, gloves, and protective suit with glasses.

Corrosion Factors

• Multiple factors determine if a material is prone to corrosion.
• Primary factors include water, iron, and oxygen.
• Factors that promote corrosion:
  • Dimensions of the part
  • Materials composing the part
  • Surface condition
  • Repair tools used
  • Contact between different metals
  • Metal composition
  • Hydrocarbon vapors
  • Pollution and dust
  • Weather Seasons
  • Storage
  • Poor repair work
  • Impact splinters

Corrosion Prevention

• Oxygen is the most favorable element to eliminate to avoid corrosion, achieved by stopping its contact with the steel surface using paint or other coatings.
• Corrosion Process from a Chemical Viewpoint:
  • Atoms in the oxidized substance release electrons.
  • Oxidizing substances receive these electrons, which results in a chemical reaction.
  • An inverse reaction is called reduction.
  • Reduced substances receive supplementary electrons.

Electrochemical Principles of Metals

• Corrosion is an electron transfer between two different materials.
• Gain of electrons is reduction, while loss of electrons is oxidation.
• Issues arise in hybrid assemblies when different materials come into direct contact, leading to electrochemical corrosion.
• Ways to isolate metals to prevent corrosion:
  • Protect with anti-rust coating
  • Apply mastic
  • Apply surfacer

Preventing Rust

• Car bodies don't rust immediately due to the zinc that oxidizes first which protects the steel from corrosion.

Electrochemical Potential of Metals

• Gold is not an element that corrodes easily.
• Steel corrodes in the presence of copper.
• Copper corrodes in the presence of aluminum.
• Zinc is not a metal corroded by manganese.
• Steel is protected in the presence of zinc.
• Aluminum oxide does not corrode lead.
• A layer of tin may protect steel from corrosion.
• Iron does not protect silver against corrosion.
• The term "rust" applies exclusively to ferrous metals, like steel, iron and cast iron.

Types of Corrosion

• Galvanic Corrosion: Occurs when potential difference between two different metals in the presence of an electrolyte is too great, leading to the inert layer covering the material beginning to decompose
• Pitting Corrosion: An isolated form that creates one or more small holes in the metal
• Inter crystalline Corrosion: Occurs between the crystals of a metal, leading to irreparable destruction of the piece