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CORROSION By: MANAN JAIN ( ) T32

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1 CORROSION By: MANAN JAIN (130010114016) T32
RENISH PIPALIYA ( ) T38 Faculty name: Patel Dipsa Institute name: Food procrssing Technology department A.D.patel institute of technology Karamsad

2 What is Corrosion? Corrosion is the oxidation of a metal due to an ELECTROCHEMICAL reaction. The oxidizing agent is most often O2 (atmospheric corrosion) or H+ (chemical corrosion) or both.

3 Requirements for corrosion
Active metal Water Oxygen (atmospheric corrosion) Acid (chemical corrosion) High temperature Corrosion Triangle Electrolyte Metal Oxidize

4 Example of Atmospheric Corrosion
Corrosion on wing of Navy aircraft F/A-18C Hornet Contrast. What exactly is shown in the pictures? Too wordy.

5 Example of Stress Corrosion Aloha Flight 243 (28 APR 1988)
Stress Corrosion Cracking tensile stress and corrosive environments cracks are initiated at corrosion areas tensile stresses propagate the crack corrosion further deteriorate crack

6

7 FORMS OF CORROSION • Stress corrosion • Galvanic • Waterline corrosion
work together at crack tips. • Galvanic Dissimilar metals are physically joined. The more anodic one corrodes. Zn & Mg very anodic. • Waterline corrosion Maximum amount of corrosion takes place beneath the surface of the water meniscus • Pitting Downward propagation of small pits & holes. 9

8 GALVANIC SERIES • Ranks the reactivity of metals/alloys in seawater
Platinum Gold Graphite Titanium Silver 316 Stainless Steel Nickel (passive) Copper Nickel (active) Tin Lead Iron/Steel Aluminum Alloys Cadmium Zinc Magnesium 8

9 Factors influencing corrosion
Nature of metal Purity of metal Temperature Humidity of air Presence of impurities in air Influence of pH

10 How do we suppress corrosion?

11 Applications of Cathodic Protection
Galvanized Steel Zinc coating Sacrificial Anodes Ship Hulls Subs (free flooding areas) Los Angeles Class Sub Arleigh-Burke Destroyer

12 Galvanizing Galvanizing is the process of coating iron or steel sheets with a thin coat of zinc to prevent them from rusting. It is most widely used for protection of iron from atmospheric corrosion in the form of roofing sheets , wires , pipe , nail , bolts , screw , bucket etc,

13 Tinning Tinning is coating tin over the iron or steel articles.
It possesses considerable resistance against atmospheric corrosion. Moreover because of non-toxic nature of tin , tinning is widely used for coating steel , copper and brass sheets , used for manufacturing containers for storing foodstuffs , ghee , oil etc. Tinned-copper sheets are employed for making cooking utensils and refrigeration equipment.

14 Corrosion Prevention Barrier films Inhibitive Pigments
Coatings Barrier films Inhibitive Pigments Sacrificial treatments Paint

15 THANK YOU


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