PHARMACEUTICAL ENGINEERING corrosion.pptx

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1. CORrOSSION Presented By:S.SIVANANTHAM B.PHARMACY Second Year (Third Sem ) AADHIBAGAWAN COLLEGE OF PHARMACY Guided By: L.GOPI M.PHARM Asst Prof Of Department Pharmaceutics Rantham

2. DEFINITION THEORIES OF CORROSION TYPES OF CORROSION FACTORS AFFECTING COROSSION PREVENTION OF CORROSION

3. DEFINITION: Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, carbonates or sulfide. It is the gradual destruction of materials by chemical or electrochemical reaction with their environment. THEORIES OF COROSSION: Acid Theory Of Corrosion: Dry or Chemical Corrosion Galvanic or Electrochemical

4. 1. ACID THEORY OF CORROSION: This theory suggests that corrosion of a metal is due to the presence of acids surroundings it. According to this theory, iron is corroded by atmospheric carbon di-oxide, moisture and oxygen. The corrosion products are the mixture of Fe(HCO3)2, Fe(OH)CO3 and Fe(OH)3.

5. 2. CHEMICAL THEORY OF CORROSION: According to this theory, corrosion on the surface of a metal is due to direct reaction of atmospheric gases like oxygen, halogens, oxides of sulphur oxides of nitrogen, hydrogen sulphide and fumes of chemicals with metal. The extent of corrosion of a particular metal depends on the chemical affinity of the metal towards reactive gas. Oxygen is mainly responsible for the corrosion of most metallic substances when compared to other gases and chemicals.

6. 3. GALVANIC OR ELECTROCHEMICAL CORROSION: It is a common type of corrosion of metal in aqueous corrosive environment. This type of corrosion occurs when the metal comes in contact with a conducting liquid or when two dissimilar metals are immersed or dipped partly in a solution. According to this theory, there is the formation of a galvonic cell on the surface act as anode and rest act as cathode.

7. TYPES OF CORROSION: 1. DRY CORROSION: Corrosion occurs in the absence of moisture. It attacks direct attack of chemicals on the metal surface. 2. WET CORROSION: Corrosion occurs in presence of conducting medium. It involves formation of electochemical cells.

8. FACTORS INFLUENCING CORROSION: The nature and extent of corrosion depend on the metal and the environment. The important factors which may influence the corrosion process are 1. Nature of the metal 2. Environment 3. Concentration of electrolyte 4. Temperature 5. Electrode potential 6. Hydrogen over voltage

9. PREVENTION OF CORROSION: Selection of proper material Proper design of equipment Coating and linings Altering environments Inhibitors Cathodic protection Anodic protection

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