Methods to control corrosion and prevent it include surface coatings, proper design of structures, using pure metals, modifying the environment, material selection, and improvements to materials. Surface coatings isolate the metal from its corroding environment and can provide protection, impact resistance, and specific mechanical and physical properties. Proper design includes avoiding sharp corners and places where water can collect, as well as preventing contact between dissimilar metals. Using pure metals prevents heterogeneity that can lead to corrosion. The environment can be modified by changing factors like temperature, oxygen levels, and inhibitor chemicals. Material selection and improvements involve choosing metals and alloys that are naturally resistant to the environment. Cathodic and anodic protection techniques use sacrificial anodes or impressed current to

1. Methods to control a corrosion
And prevention

2. Introduction
The process of decay of metal by environment
attack is called corrosion.
For example=
A) Formation of reddish brown layer of rust on the
surface of iron.
B) Formation of green film of basic carbonate on the
surface of copper.
The corrosion of metals is measured in the units of
milliinches/year or mm/year.

3. Causes of corrosion

4. Methods of corrosion control
● surface coating
● proper designing
● use of pure metal
● Modifying theenvironment
● Material selection
● Improvements of material
● cathodic & anodic protection

5. Surface coatings
● The common and oldest method of protection of a
metal from its surrounding by surface coating
● These may be
1). Metallic coatings
2). Organic coatings
The coated metal isolate the metal from its
corroding environment

6. Function of metal productive coating
● To protect the metal from the corrosion.
● Impact assisting sense on metal surface.
● To impact specific mechanical, physical
and electrical properties.
● To give oxidation resistance and thermal
insulating propoties.

7. Design of structures
● Avoid sharp corners
● Complete draining of vessels
● No water retention
● Avoid sudden changes in section
● Avoid contact between dissimilar metals
● Weld rather than rivet
● Easy replacement of vulnerable parts
● Avoid excessive mechanical stress

8. Using pure metal
● Impurities cause heterogeneity
● Thus use of pure metals prevents corrosion
● Use non - Corrosive metals, such as stainless steel or
aluminum.
● Use high melting point metals
{-----Pure metals can’t get roast

9. Alternation of environment
● Lower temperature and velocity
● Remove oxygen/oxidizers
● Change concentration
● Add Inhibitors
- Adsorption type ,e.g. Organic amines,azoles
- H evolution poisons,e.g. As & Sb
- Scavengers, e.g. Sodium sulfite & hydrazine
- Oxidizers,. e.g chromates,nitrates, ferric salts

10. Material selection
● Most important method - select the appropriate
metal or alloy.
● Natural” metal-corrosive combinations like
● S.S.- Nitric acid,Ni & Ni alloys- Caustic
● Monel- HF, Hastelloys- Hot HCl
● Pb- Dil. Sulphuric acid, Sn- Distilled water
● Al- Atmosphere, Ti-hot oxidizers
● Ta- Ultimate resistance

11. Improvements of Materials
● Purification of metals- Al, Zr
● Alloying with metals for: making more noble ,e.g.Pt in Ti
● Passivation, e.g. As & Sb in brass
● Scavenging, e.g Ti & Nb in S.S
● Improving other properties

12. ● Solvent cleaning :- Removes oils ,grease, & fatty
substance by the organic solvent like naphtha,
CCl,toluene, acetone. Then the metal surface is cleaned
with steam & hot water containing westing reagents

13. ● Alkalin cleaning:- Removes old paint-alkali
cleansing agents like trisodium phosphate along
with soaps and wetting agents.

14. ● Sand blasting :- Removes oxide scales- sand of
different grain size were blasted on the metal
Surface with pressure of 25 100atm

15. Cathodic protection
● The metal to be protected each connected to an external
and a DC current is pass so that all areas of the metal surface
become catholic and do not carrode.
● Cathodic protection can be achieve into ways:
1) By sacrificial Anodes.
2) By Impressed Current.

16. Sacrificial Anodes
● These Anodes consist of the highly reactive metal like Mg.
● To protect pipes, rods or Mg Buried near the pipes and
connected to them by wires.
● The galvanic cells with high E.M.F are set up with surface to
be protected made cathodic.
● The cost of replacement of corroded anodic Mg is much less
than the replacing pipe

17. Reference
● Test book of polytechnic engineering chemistry by := R
Gopalan,
● Msbte chemistry book
● Lecture notes by Mayuri borse mam
● Google
● Wikipedia
● Corrosion.ksc.nasa.org

18. Thank you