IntroductionWhy do we paint steel? Updated November 2005
Why do we need to paint steel? By far the single most importantreason is to protect a huge financialinvestment by means of CorrosionPrevention. Ships, factories, oil refineries etccost millions of dollars to build – wecan not just let them rust away.
What is CorrosionCorrosion is basically:-“The attack on metals by their environment.”We normally see it as steel changing to rust.Nature is simply returning steel from an unstable man-made state to a stable natural state.
Corrosion STEEL Iron Metal Chemically Unstable Structural HEAT CORROSION (By Man) (By Nature) Chemically the same! IRON ORE RUST Iron Oxide Iron OxideChemically Stable Chemically Stable Non-Structural Non-Structural
Corrosion • Steel corrodes… • Rust is weak… • Rust is porous… • Rust detaches from the steel… • Rust does not prevent more corrosion……..…SO WHY USE STEEL?
Why use Steel?• Iron ore is very widely available.• It is easy to make steel from iron ore• Steel is strong relative to its weight• STEEL IS CHEAP!!!!!
FoulingShoreline animals released as tiny larvae:- • Hydroids - can swim for just a few hours • Barnacles - can swim for up to 6 weeks…if they do not find a surface to colonise in thattime they die.
Why do we use Antifoulings?We are used to the idea of fast moving items having to be streamlined to go smoothly through air
Why do we use Antifoulings?……but the same principles apply for ships passing through water – albeit at much slower speed.
Why do we use Antifoulings?Drag on ships comes from roughness due to corrosion & fouling! Although a barnacle seems very small compared to a ship, if there are enough of them, it will greatly increase fuel costs.. BECOMES
Fouling controlShell Fouling: Up to 40% increase in drag
The Fouling Challenge POLAR• Temperature TEMPERATE• Pollution TROPICAL/SUBTROPICAL• Nutrients EXTREME FOULING ENVIRONMENT
Marine vs PC• We do not use the same coatings for both Marine & PC tanks.• PC Tanks hold one chemical for many years.• Marine Tanks hold cargoes for short periods and then have to be able to carry a totally different cargo.
Why do we need to paint steel?1) Corrosion Prevention2) Fouling Control3) Cosmetic Appearance4) Cargo Storage / Carriage5) Abrasion Resistance
Abrasion Resistance Ice abrasion removes all coating from outer hull
Abrasion Resistance An ice-breaker hull protected by a special anti-abrasion coating.
Why do we need to paint steel?1) Corrosion Prevention2) Fouling Control3) Cosmetic Appearance4) Cargo Storage / Carriage5) Abrasion Resistance6) Skid Prevention
Skid PreventionWould you like to be working on this deck?
Skid PreventionGood grip is essential to land a plane on a deck
Why do we need to paint steel?1) Corrosion Prevention2) Fouling Control3) Cosmetic Appearance4) Cargo Storage5) Abrasion Resistance6) Skid Prevention7) Fire Protection8) Radar Absorption9) Heat Resistance10) Low Solar Absorption
Radar Absorption• Some navies require special coatings for above-water areas to make them ‘invisible’ to radar.• These are very specific types of coatings for each navy and developed in great secrecy.