CORROSION

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CORROSION

• The University of Technology Brno, School of
  chemistry

20.4.2005 Pavel Haška
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Something about corrosion

• When was rust define?
• In 30th years 20th century.
• Whats heart of corrosion?
• Physical-chemical destruction of materials by
  ambient enviroment.
• How is corrosion defined?
• Spontaneous non-reversible proceed sequential
  erosion of materials by physical-chemical ambient
  enviroment.
• What corrode the rust?
• just about all materials, not only metals and
  their alloy, but non-metal materials, as ceramic
  and silicated anorganic matter (glass, concrete),
  or organic matter (rubber, plastic materials) and
  other materials
• How influence the corrosion?
• 3 basic factors material, corrosion rate,
  medium of corrosion

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Metal corrosion

• When rust proceed ?
• energy primary component of sys corrostion is
  higher as energy product of corrosion
• Just about all metals are unstable from
  thermodynamic view, mainly technical metals.
• How corrosion show ?
• loss of material and creation corrosive
  products, material changes (loss of strength and
  ductulity, birth of microcrack). Some changes are
  showed, when time expiry.

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Type of corrosion

• Uniform corrosion
• Nonuniform corrosion
• Stain corrosion
• Pitting corrosion
• Point corrosion
• Undersurface corrosion
• Selective corrosion
• Intergranular corrosion
• Transgranular corrosion
• Extraction corrosion
• Crack of corrosion

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UNIFORM CORROSION
NONUNIFORM CORROSION
STAIN CORROSION
PITTING CORROSION
POINT CORROSION
UNDERSURFACE CORROSION
SELECTIVE CORROSION
INTERGRANULAR CORROSION
TRANSGRANULAR CORROSION
EXTRACTION CORROSION
CRACK OF CORROSION
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Rust protection

• Form corroding medium
• Choice of available material
• Model solution
• Manufacturing technology
• Electrochemical cover
• Surface treatment

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Surface treatment

• katodic protect (e.g. zinc coatings in steel)
• we can enrich surface of metal by alloying
  elements (e.g. hot chromizing, alumining)
• coating isolate protect surface against corrosion
  medium (e.g. corrosion protective paint and
  plastics, coatings from tin in steel)
• synthetic compound layer of protect metal has
  better protective properties (e.g. phosphated
  coatings in steel, oxidized coatings in
  aluminium)
• layer of matter has inhibic effect for protective
  metal (e.g. chromate treatment of zinc, inhibic
  basic paint)

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In conclusion

• Metals are used in all world for many years.
  Plastic materials are substituted step by step,
  but the metals play always perform in models and
  other branches, we can used in common life. Some
  metal are recyclable. They are used, because are
  economic favourable.
• Protect of steel is still evolvic branch. Every
  day create new techniques for protect against
  corrosion.

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Thank you for your attention?