Corrosion & Corrosion engineering

and cathodic protection method

 Group #7
Topic: Corrosion and its types ( general overview related to E&P activities)
Group Members

Sherullah Khan 2k16-P&G-26

Yasir Khan 2k16-P&G-25
Ali Usama 2k16-P&G-12
Usman Kathia 2k16-P&G-21
Jawad Aslam 2k16-P&G-26
Corrosion:
• Corrosion is the process by which something damage because of
oxidation,that flake away from base.
• Although the word is most often associated with physical breakdown
of a metal through rusting.
• The erosion of rock by wind and water is a form of corrosion.
• It is the oxidation process. It causes loss of metals.
• For example:
1. Formation of rust on the surface of iron.
2. Formation of green film on the surface of copper.
Corrosion:

Disintegration of a metal
by its surrounding
chemical through a
chemical reaction on the
surface of metal is called
corrosion.
Corrosion engineering:
Corrosion engineering is the specialist discipline of
applying scientific knowledge, natural laws and
physical resources in order to design and implement
materials, structures, devices, systems and procedures
to manage the natural phenomenon known as
corrosion.
Who will study corrosion??
Reason’s for corrosion study:

• Economic (due to material losses).

• Safety (to prevent catastrophic consequences resulting from

operation failure of equipment).

• Conservation ( to conserve metal resources, which are

limited).
Four requirements of corrosion:
• Anode
• Cathode
• Current flow
• Electronic path
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:
(i) Nature of metal
(ii) Environment
(iii) Concentration of electrolyte
(iv) Temperature
(v) Electrode potential
(vi) Hydrogen over voltage
Forms of corrosion:
• General:
Identified by uniform formation of corrosion product.
• Localized:
Caused by different chemical or physical conditions.
• Bacterial:
caused by formation of bacteria that has infinity to metal.
• Galvanic/Dissimilar metal:
Caused when dissimilar metals come to
contact.
Types of corrosion:
There are basically eight types of corrosion.

(i) uniform corrosion

(ii)Pitting corrosion
(iii)Transgranular or intergranular
(iv)Exfoliation corrosion
(v) Stress corrosion
(vi) Crevice corrosion
(vii)Galvanic corrosion
(viii)Erosion
Uniform corrosion:
• This type of corrosion develops as pits of very small diameter, in the
order of a micrometer.
• It results in a uniform and continuous decrease in thickness over the
entire surface area of the metal.
• The rate of uniform corrosion can be easily determined by measuring
the mass loss, or the quantity of released hydrogen.
Pitting corrosion:
• This localized form of corrosion is characterized by the formation of
irregularly shaped cavities on the surface of metal.
• Their diameter and depth depend on several parameters related to
the metal, the medium and service conditions.
• Pitting corrosion can be assessed using three criteria: the density i.e.
the number of pits per unit area, the rate of depending and the
probability of pitting.
Transgranular and Intergranular Corrosion:
• Within the metal, at the level of the grain.
• It spreads in all direction, it effects all the metallurgical constituents:
there is no selective corrosion. It propagates within grains.
• It is not detectable with naked eye, but require microscopic
observation.
Exfoliation corrosion:
• It propagates along a large number of planes running parallel to the
direction of rolling or extrusion.
• It occurs along aluminium grains.
Stress corrosion:
• This type of corrosion results from the combine action of a
mechanical stress (bending, tension) and a corrosive environment.
• Each of these parameters along would not have such a significant
effect on the resistance of the metal.
Crevice corrosion:
• Crevice corrosion is a localized corrosion in recesses:
• Overlapping zones for riveting, bolting or welding, zones under joints
and under various deposits. These zones also called crevice.
• This type of corrosion is also known as deposit attack.
Galvanic corrosion:
• When two dissimilar metals are in direct contact in a conducting
liquid, experience shows that one of the two may corrode. This is
called galvanic corrosion.
• The other metal will not corrode; it may be protected in this way.
Galvanic corrosion may occur with any metal.
Erosion:
• Corrosion by erosion occurs in moving media. This type of corrosion is
related to the flow speed of the fluid.
• It leads to local thinning of the metal, which results in scratches,
undulations, which are always oriented in the same direction, namely
the flow direction.
Corrosion rate expression:
• mm/y- millimeter penetration per year
• gmd- grams per square meter per day
• ipy-inches-penetration per year
• mpy- mils penetration per year

• Corrosion rate<0.005ipy (good corrosion resistance).

• 0.005<Concentration rate<0.05 ipy (satisfactory).
• Concentration rate> 0.05 ipy (unsatisfactory).
Consequences of corrosion:
• Waste of metals
25% of annual world production of iron is wasted due to
corrosion.
• Decrease in efficiency of machineries
• Failure of machineries
• Leakage in the process
• Health & fire hazard
• Causes contamination
Corrosion Prevention:
• How to do this???
• Change the metallic material.
• Altering the corrosive environment (Ph, acidity, temp)
• Separating the metal from environment (insulation).
• Provide appropriate design.

Other aspects of corrosion prevention:

• Welding is preferable from riveting
• Easy drainage and cleaning (design aspects).
• Avoid sharp bends
• Avoid electric current
Cathodic protection:
• Cathodic protection is a method of corrosion control that can be
applied to buried and submerged metallic structures.
• It is considered as a secondary corrosion control techniques.
• Cathodic protection can, in some cases, prevent stress corrosion
cracking.
 Principal involved:

• The principal of cathodic protection is to prevent anodic sites

occurring on the structure under protection by allowing the anodic
reactions to occur on specially designed and installed anodes.
History:
• Cathodic protection was first described by sir Humphry davy in a
series of paper in London 1824.
• Thomas Edison experimented with impressed current cathodic
protection on ships in 1890. but he was unsuccessful due to lack of
current source.
• In the USA by 1945 the use of Cp was commonly applied to the rapidly
expanding oil and gas industry
• Cp is now well established on large variety of immersed and buried
metallic structure as well as concrete structure.
Description of CP:
• The simplest method to apply cp is by connecting the metal to be
protected with another more easily corroded “sacrificial metal” to act as
anode of the electrochemical cell.
• The sacrificial metal then corrodes instead of the protected metal, for
structure where passive passive galvanic CP is not adequate, for example in
long pipelines, an external DC electrical power source is sometimes used to
provide current.
• Cathodic protection system are used to protect a wide range of metallic
structures in various environments. For example in offshore oil platforms
and onshore oil well casing and metal bars in concrete buildings and
structures.
• Another common application is in galvanized steel, in which a sacrificial
coating of zinc on steel parts protects them from rust.
Cathodic protection (CP):
• Basics of cp:
• External electric current is applied.
• Cathodic potential is lowered to anodic direction.
• Corrosion current no longer flows.
• Surface becomes equipotential.
Cp cannot be used- where???

• In nonconducting liquids (oil).

• In extremely corrosive environment.
(theoretically possible but incurs huge cost)
• In electrically screened areas.
• In vapor
How does it work???
• Simply cp works by preventing the anodic reaction of metal
dissolution occurring on the structure.
Cp with sacrificial anode:
• Direct connect with a more active metal.
• Anode of this system is called sacrificial anode.
Cp with sacrificial anode:
• Sacrificial anode is useful when no electrical power is available.
• Low cost installation.
• Low maintenance cost.
• Combination with coating is better.
Work picture of CP:
Cathodic anode:
Internal CP:
• Vessels, pipelines and tanks which are used to store or transport
liquids can also be protected from corrosion on their internal surfaces
by the use of cathodic protection.
Application of cathodic protection:
• 1.pipelines:
pipelines are routinely protected by a coating
supplemented with cathodic protection.
Ships:
Cathodic protection on ships is often implemented by
galvanic anodes attached to the hull.
Other application of CP:
• Underground tanks
• Structures e.g bridges
• Evaporators
• Valves, piping and other metal surfaces
Purpose of corrosion testing:
• To evaluate and select materials.
• To obtain reference or database information.
• To determine quality control and material acceptance requirement.
• To monitor corrosion-control programs.
• To identify research parameters and corrosion mechanisms.
Testing inspection and monitoring:
Some examples:
Examples of corrosion:
Household examples:
Household examples:

Mop pipe
Cont’d…

Corrosion on Iron pipe

Cont’d…

Corrosion on water cooler stand

Corrosion in petroleum industry:
• Production of petroleum industry. corrosion of metal in the presence
of water is a common problem across many industry. The fact that
most oil and gas…
• Corrosion cost the oil industry billions of dollars a year. Corrosion
effects every aspects of exploration and production, from offshore
rigs.
• Determines the yearly cost of corrosion for specific industry sectors:
Petroleum refining. 0.1B$
Oil and gas exploration & production 1.4B$
Reasons of corrosion in petroleum industry:

• In petroleum industry at high temperatures, H2S attacks steel foaming

Fes scale which is porous and interferes with normal operations.
• Sour gas condensate corrosion in refinery heater tubes.
• Internal corrosion due to multiphase flow in the pipeline.
• Severe corrosion rate caused by CO2 and hydrate in the gas lines.
Corrosion control techniques in oil industry:
• Design corrosion strategies for maintaining of pipelines.
• Systematic approach to implementing cathodic protection to minimize
external pipeline corrosion.
• The important of internal corrosion rate monitoring before and after
chemical injection and treatment.
• Downhole tubing and casing calipers, ultrasonic wall thickness testers
and radiography.
• Removal of dissolved corrosive agents and non hydrocarbons gases in
the gas, oil and produced water fluids.
Conclusion
Corrosion costs of the oil industry are billions of dollars in
a year. Corrosion affects every aspect of exploration and
production, from offshore rigs to casing. Recently, the methods and
techniques to control corrosion gain momentum in this area.
Expectation from you????
Thanks for your attention