1. Physical Science Applications in Agriculture Unit Physical Science Systems

2. Problem Area Agricultural Mechanics and Machine Systems

3. Corrosion and Rust Removal Lesson

4. What is a rust? Display several items that are severely corroded. Describe the best way to remove the rust from these items. Can they be restored to their original quality? Indicate where each item has been stored/used. What factors affect the rate of corrosion of metals?

5. Learning Objectives 1.Explain what chemical processes are involved in rust formation. 2.Identify the factors or conditions that intensify corrosion. 3.Explain how an electrochemical process can be effective in removing rust. 4.Identify ways to prevent metals from corroding.

6. Terms Corrosion Electrolyte Ionization Iron Oxidation Oxide Reduction Rust www.papercreek.com/texture.html

7. What chemical processes are involved in rust formation? Because it is strong, malleable, and relatively abundant, iron is widely used in the manufacturing of many products upon which we depend for comfortable living. www.geo.msu.edu/geo333/iron.html

8. What chemical processes are involved in rust formation? Corrosion is an everyday problem in agricultural structures, machinery, tools, and equipment. However, corrosion cuts the life, value, and appearance of machinery, tools, and many other work and recreational items. In warm, moist climates corrosion takes a heavy toll, creating both economic and recreational losses.

9. What chemical processes are involved in rust formation? Corrosion is the destruction, degradation, or deterioration of material due to the reaction between the material and its environment 1.Corrosion is a chemical or electrochemical reaction. 2.Corrosive agents are classified as oxygen and oxidants, acidic materials, salts and alkalis.

10. What chemical processes are involved in rust formation? Corrosive reactions between metals and gases consume the metal and change the metal’s properties. 1.Corrosion by gases leaves the products of corrosion on the surface of the metal, leaving a protective film in some cases. 2.Local electrochemical reactions are suppressed when corrosion is by gases. 3.Corrosion by liquids leaves corrosion products with higher electrochemical reactions that do not tend to leave a protective film on the metal.

11. CORROSION Destruction, degradation, or deterioration of material due to the reaction between the material and its environment A chemical or electrochemical reaction Reactions between the metal and gases consume the metal and change the metal’s properties

12. What are the factors and conditions that intensify corrosion? There has been much time and money spent on developing and using rust prevention materials and techniques. A.Metals can be grouped according to their corrosion resistance. 1.The first group includes metals such as iron, a widely used, heavy, magnetic metal; that does not form completely protective corrosion products.

13. Metals 2.The next group includes metals such as aluminum and brass that become resistant to attack, due to the formation of a corrosion resisting film. 3.The third group is almost completely resistant to corrosion and includes gold, stainless steel, and chromium.

14. What are the factors and conditions that intensify corrosion? Corrosive reaction is often limited by formation of a thin oxide, a binary compound in which oxygen is combined with a metal or nonmetal film. This limits the access of oxygen, water vapor, and other gases. 1.In dry atmospheres the oxide film remains intact. 2.In humid conditions the oxide film breaks down and hydrated oxides are formed.

15. What are the factors and conditions that intensify corrosion? Rust –Product of the oxidation of iron or its alloys and is due either to atmospheric attack or electrolytic effect of corrosion cell action around impurities. www.nc911.com/Misc-Photos/stormchasing9-15.htm

16. What are the factors and conditions that intensify corrosion? A corrosion cell is a condition on a metal surface in which a flow of electrical current occurs between the metal surface and an electrolyte, a chemical which conducts current through ionization, with which it is in contact. Ionization is the formation of ions by separating atoms or molecules, by adding or taking away electrons from atoms or by weakening electron attraction in a liquid.

17. What are the factors and conditions that intensify corrosion? This current is sufficient enough to cause the metal to degrade. Corrosion cells are microscopic electrochemical spots on the metal surface where metal dissolves at weak spots in the oxide film.

18. How does an electrochemical process remove rust? In rust formation iron (Fe) changes into ferrous ion (Fe2+), leaving two free electrons in the metal. This is the anodic (destructive) reaction. These electrons pass through the oxide film; combine with oxygen from the air and water to form hydroxyl ions, the cathodic reaction. When the ferrous ions meet the hydroxyl inks (2OH-), a solid product is formed that soon becomes rust. Rust is a complex, hydrated form of iron oxide (Fe2O3).

19. How does an electrochemical process remove rust? In the corrosion of iron, rust is formed in a two- stage (oxidation-reduction) reaction. Oxidation and reduction occur simultaneously and in equivalent amounts in any reaction involving either process. 1.Oxidation involves the loss of electrons from an atom and it involves the addition of oxygen to the compound. 2.Reduction involves the absorption of electrons by another compound.

20. How does an electrochemical process remove rust? In electrolytic connectors, such as water, the positively and negatively charged ions move in opposite directions and each carries a portion of the electrical current through the solution. www.theaa.com/allaboutcars/flat_battery_advice.html

21. How does an electrochemical process remove rust? A battery charger sends electrons into the electrolyte solution at the anode (negative lead). Ions travel through the water from the negative lead to the positive lead, thus removing electrons from the rust and causing it to break down.

22. How does an electrochemical process remove rust? The amount of chemical charge produced by an electrical current is proportional to the quantity of electricity passed through the solution.

23. What can be used to prevent metals from corroding? The following protective coatings can help prevent rust: – Paints – Lacquers – Primers – Oils – Waxes www.bristoldoor.com/.../ rust_proof.htm

24. Review/Summary What are the factors and conditions that intensify corrosion? How does an electrochemical process remove rust? What can be used to prevent metals from corroding?