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EP321

Corrosion

Semester May

Aug 2013

Assignment: Safe estimation of corrosion

STUDENT NAME : Tan Chern Yee

STUDENT ID : 1000922102

DATE OF SUBMISSION : 18-07-2013

PROGRAM ENROLLED : B.Eng (Hons) Chemical Engineering

SCHOOL OF ENGINEERING

FACULTY OF ENGINEERING, ARCHITECTURE & BUILT ENVIRONMENT

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Safe estimation of corrosion

Corrosion is the constant state of destruction that material undergoes by reaction to the

environment. This is because metal has a tendency to revert to its original states which is more

stable. In chemistry corrosion can also be known as an electrochemical reaction which consist of

a oxidation and reduction reaction (redox). The metal that corrodes is the one that undergoes

oxidation where the metal reacts with the environment to form metal oxides or salts of its

original state. Hence, it is better for engineers to have a safe estimation of corrosion when

designing and construction of a project.

There are several factors that can affect or cause metal to corrode. The most common form of

corrosion is general or uniform corrosion due to metal being exposed to the environment. While

it is the most common cause of corrosion it is also the easiest to detect and prevented. Hence, in

order prolong the lifetime and ensuring the safety, all metallic surfaces must be painted with

corrosion prevention coatings. Besides coatings, when designing a project corrosion allowance is

a must to be considered as corrosion occurs the thickness of metal decreases with time and

failures may occur due to stress subjected to the compromised section due to corrosion over time.

The other more common form of corrosion is galvanic corrosion which can be due to galvanic

corrosion. This occurs when there is a potential difference between two dissimilar metals. The

further apart both metals in the galvanic series the high the potential which means the faster the

corrosion rate when two dissimilar metals are placed together. Thus, as a thumb rule when

designing a project dissimilar metal part is to be avoided at all cost. This can also occur between

metals and the environment.

The most dangerous form of corrosion is the localized corrosion where it can happen rapidly and

suddenly due to various reasons where the affected area is random. Various form of localized

corrosion are pitting, crevice and filiform corrosions. Localized corrosion occurs randomly on

the surface area of metals. Thus, frequent inspection on working equipment and structure of

building where the metallic parts are exposed is a must to be conducted in order to maintain a

safe working environment.

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In any industry the working environment may differ from one workplace to another. This is due

to the contaminant or by-product that is released to during the production process. As engineers,

this has to be taken into account when doing the selection of material together with the

estimation of the effects of corrosion and the preventive step to be taken before corrosion takes

place and damages any structure or equipment.

While corrosion can be happen due to many external factors, design also plays an important role

in corrosion. This is because there are types of corrosion that occurs due to designs flaw for such

as sharp turning or junction in a design. This type of turning can cause concentration cell type

corrosion due to design flaws and improper joint such as riveted and bolted joints. While

designing aspect may cause corrosion to occur, manufacturing flaws such as crevices from

improper welding too can cause corrosion to occurs. Thus, crevices and unnecessary gaps must

be welded properly to prevent concentration cell based corrosion.

While prevention can only do so much proper maintenance and regular maintenance is important

in order to spot corroded segments of the equipment used or detect structural flaws and thinning

of structure due to corrosion. It is also important to clear out deposit of corroded metals and treat

the affected if possible before corrosion spreads any further and causes damage. Therefore, in

order to safely estimate the effects of corrosion, the several factor to take note are :

Thickness of corrosion allowance for intended life expectancy of equip Reactiveness of working environment towards metals Resistant of metals towards corrosive elements Wear and tear (stress) towards equipment causing erosion corrosion Inspection of stagnant areas of equipment Ensure any crevices or gap formed are seal immediately Presence of other type of working equipment based on different metal species Design flaws that maybe prone to corrosion Whether reactant used will react with the metal of the equipment

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References

http://www.nace.org/Newsroom/Press-Releases/How-to-Improve-Pipeline-Safety-Through-

Corrosion-Management/

http://www.corrosion.org/

http://corrosion.ksc.nasa.gov/electrochem_fundamentals.htm

http://en.wikipedia.org/wiki/Corrosion

http://www.tis-gdv.de/tis_e/misc/korro.htm

http://metals.about.com/od/metallurgy/a/Corrosion-Prevention.htm

http://www.corrosion.org/http://www.corrosion.org/http://corrosion.ksc.nasa.gov/electrochem_fundamentals.htmhttp://corrosion.ksc.nasa.gov/electrochem_fundamentals.htmhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Corrosionhttp://www.tis-gdv.de/tis_e/misc/korro.htmhttp://www.tis-gdv.de/tis_e/misc/korro.htmhttp://www.tis-gdv.de/tis_e/misc/korro.htmhttp://en.wikipedia.org/wiki/Corrosionhttp://corrosion.ksc.nasa.gov/electrochem_fundamentals.htmhttp://www.corrosion.org/