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http://www.brighthub.com/engineering/marine/articles/66980.aspx

Corrosion protection of our ships in the marine environment has challenged us

for years in the areas of their hulls and internal tans! the use of coaltars beingprevalent. "owadays however there are many innovative types of epoxycoatings and speciali#ed paints available to combat corrosion attac

$hips and offshore structures re%uire protection against the marineenvironment. &his protection is re%uired above and below the waterline as wellas the splash #one in offshore structures! being exposed to both air and li%uidassault.

$torage tans such as fresh water and ballast tans also re%uire special internalanti'corrosive coating as do the oil storage tans in oil taners.

&he properties and applications of these coatings are provided by guidelines!rules! and regulations set out by governing bodies such as $()*$ and the+,(.

-epending on their particular application! corrosive resistant coatings can besupplied in various categories such as paint and epoxies.

&his is an article on the protection of ships against corrosion! here we willexamine the potential damage caused by the corrosive marine environment.

e begin by having a loo at the different areas of these vessels! go on toexamine the different types of protection available.

Susceptible Areas

&hese areas are listed below:

Hulls

&his includes the area above and below the waterline and can sometimes be

combined with an anti friction coatings on the hull below the waterline.

Decks

-ecs liable to corrosion due to salt being deposited on the plating and also dueto the wearing of the coating due to dec'wor

Tanks

allast &ans

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allast tans are very susceptible to corrosion due to their constant wet and dryconditions when the ship is ballasted or carrying a full cargo.

allast tans have been in the news regarding the spreading of non'indigenousseawater borne marine bacteria! organisms and barnacles. Coatings to

eradicate these have been developed and are applied after a coating of anticorrosive material.

reshwater $torage &ans

&hese tans used to be cement washed and then chlorinated to preventcorrosion and protect against 1'Coli and )egionnaires disease. ,ore modernmethods are available today.

Treatment of Susceptible Areas

Hulls

*rea elow the aterline

&his underwater area is protected from corrosion following the hull constructionbefore it is launched. (ne of the more popular protection used is two part coal'tar epoxy in con2unction with a vinyl tar coat.

&his combination has been found satisfactory and can be repaired at the shipsyearly drydoc survey.

Decks and Hulls Above the Waterline.

$hips decs are also liable to corrosion due to being immersed in seawaterduring adverse weather depositing salt on the plating. hen + was at sea thesailors were forever chipping away and repainting the dec or hanging over theside in a bosun3s chair! attacing the hull. &his was not complimentary to myafter lunch snoo#e before going on the 4'8 watch.

*nyway! protection of dec and above waterline areas is carried out using a welltested combination of alyd and chlorinated rubber.

Tanks

allast &ans

allast tans are very susceptible to corrosion due to constant humiditypromoted by their surface wet and dry conditions depending if the ship isballasted or carrying a full cargo.

allast tans have been accused of being the importer and spreading of non'

indigenous seawater borne marine bacteria! organisms and barnacles. Coatings

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to eradicate these have been developed and are applied after a coating ofanticorrosive material.

allast tans used to be coated with coal tar epoxy 5C&1 but now epoxyproducts produced in hydrocarbon refining has been developed. &his is applied

in two coats and is one of the current methods used against corrosion in ballasttans.

reshwater $torage &ans

&hese tans used to be cement washed and then chlorinated to preventcorrosion and protect against 1'Coli and )egionnaires disease. + well rememberthe taste of the newly bunered fresh water after the mate had liberally dosed itwith chlorine. 7uc "ot nice in afternoon tea! to say nothing about the rum

"owadays an application of pure epoxy! applied under strict guidelines by an

experienced contractor is one method. &his can be supplemented with a strictlycontrolled addition of silver nitrate or chlorine to the tan being used to controlany bacteria in the water.

Cargo &ans

&his is a vast sub2ect due to the various cargoes carried by today3s merchantvessels from crude oil to chemicals! so will cover this fully in a future article onCargo &an rotective Coatings.

owever! in the interim we will have a %uic loo at t

he protection of oil storage tans in a crude oil taner. &he corrosion in theseareas is caused by the sulphurous and water contained in the crude! combinedwith other water vapour and the flexing of the ship3s structure. ,icrobes alsocompliment corrosion as they ingress into the protective coating. &he new hightensile steels used in ships construction and the innovation of double hulledvessels has had a detrimental effect on tans! being sited to have exacerbatedcorrosion and pitting instances.

Crude oil tan internals can be protected by applications of Coal tar and pure

epoxy coatings.

*nyway + will leave it there as + am coming bac to this sub2ect in a later article.

ebsites ;isited

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