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TRAINING AND CERTIFICATION DAI DUNG COMPANY LONG AN PROVINCE Oct, 2015 GHANA PROJECT - TRAINING SCHEDULE (Oct – 2015) 15:00 – 15:15 Basic Corrosion and Anti-Corrosives 15:15 – 15:30 Classification of Paints 15:30 – 15:45 Surface Preparation 15:45 – 16:00 Paint Application 16:00 – 16:15 Quality Control 16:15 – 16:30 Paint Film Defects - Cause and Prevention 16:30 – 17:00 Training Review: Question & Answer GIỚI THIỆU CƠ BẢN VỀ ĂN MÒN & PHƯƠNG PHÁP CHỐNG ĂN MỊN BASICS OF CORROSION & Ăn mịn/rỉ ? What is corrosion? Định nghĩa: Definition Là thoái hóa vật liệu phản ứng với mơi trường xung quanh phản ứng với hóa học hay điện hóa An undesired degradation of materials by reaction with surrounding media through chemical or electrochemical reaction Ăn mịn/rỉ ? What is corrosion? VẬT LIỆU THÉP + KHƠNG KHÍ+NƯỚC -> RỈ STEEL + AIR + WATER -> RUST 2Fe + O2 + 2H2O -> Fe(OH)2 Ăn mịn/rỉ ? What is corrosion? Air (O2) Water (H2O) Atmospheric corrosion Steel (Fe) 2H2O + O2 + 4e- -> 4OHFe++ e- Cathode 2Fe++ + 4OH- -> 2Fe(OH)2 e- Fe++ Fe Anode e- e- Cathode 2Fe(OH)2 + H2O + ½O2- -> 2Fe(OH)3 Ăn mịn/rỉ ? What is corrosion? Air (O2) Water (H2O) Steel (Fe) Copper (Cu) Galvanic corrosion 2H2O + O2 + 4e- -> 4OHFe++ Fe++ Fe Anode 2Fe++ + 4OH- -> 2Fe(OH)2 e- e- Cathode 2Fe(OH)2 + H2O + ½O2- -> 2Fe(OH)3 Ăn mịn/rỉ ? What is corrosion? GALVANIC SERIES IN SEAWATER Noble Ignoble Graphite Gold Titanium Stainless steel (passive) Bronze Copper Millscale Brass Stainless steel (active) Iron (Steel) Aluminium Zinc Magnesium Ăn mịn/rỉ ? What is corrosion? Air (O2) Corrosion in an acidic environment Acidic solution (H+) Steel (Fe) 2H+ + 2e- -> H2 Fe++ e- Cathode e- Fe++ Fe Anode e- e- Cathode Ăn mịn/rỉ ? What is corrosion? Relative corrosion rate CORROSION OF STEEL IN SODIUM CHLORIDE SOLUTIONS 0 10 15 20 25 30 Concentration of sodium chloride, weight% Weight-% of sodium chloride in sea water is… 4!!! Sea water is an ideal solution to facilitate corrosion Sacrificial anodes They prevent or decelerate the rate of corrosion by supplying the steel with electrons “sacrificially” through metal-to-metal contact GALVANIC SERIES IN SEAWATER Noble Fe e- Fe++ Zn e- ½O2 + H2O -> 2OH- Zn++ ½O2 + H2O -> 2OH- Zn Zn Zn Zn Ignoble Graphite Gold Titanium Stainless steel (passive) Bronze Copper Millscale Brass Stainless steel (active) Iron (Steel) Aluminium Zinc Magnesium What is an anti-corrosive? The term used to describe a coating or substance that protects steel, preventing it to corrode In general an anti-corrosive can work through different principles Barrier effect Inhibitor effect Galvanic effect What is an anti-corrosive? BARRIER EFFECT Leafing pigments Film thickness KẾT THÚC CÂU HỎI & TRẢ LỜI Q&A ... and Prevention 16:30 – 17:00 Training Review: Question & Answer GIỚI THIỆU CƠ BẢN VỀ ĂN MÒN & PHƯƠNG PHÁP CHỐNG ĂN MÒN BASICS OF CORROSION & Ăn mịn/rỉ ? What is corrosion? Định nghĩa: Definition... chemical or electrochemical reaction Ăn mịn/rỉ ? What is corrosion? VẬT LIỆU THÉP + KHƠNG KHÍ+NƯỚC -> RỈ STEEL + AIR + WATER -> RUST 2Fe + O2 + 2H2O -> Fe(OH)2 Ăn mịn/rỉ ? What is corrosion? Air... Magnesium Ăn mịn/rỉ ? What is corrosion? Air (O2) Corrosion in an acidic environment Acidic solution (H+) Steel (Fe) 2H+ + 2e- -> H2 Fe++ e- Cathode e- Fe++ Fe Anode e- e- Cathode Ăn mịn/rỉ ?