Materials of shipbuilding for seagoing chemical tankers
Iron, steel Mild steel and high tensile steel is, and will continue to be the most important material in the building of chemical tankers and their cargo tanks.
Steel is attacked by only a few products, mainly acids and, of course ballast and washing water. Steel itself contaminates very few products, one of them being high purity caustic soda. Rust, however, creates many problems with cargo contamination.
Rust may contaminate a product in the form of minute particles staying suspended in viscous heavy liquids such as glycols and caustic soda. Rust may accelerate polymerization in polymerizable products. Rust will be soaked in with remains of previous cargoes, mainly from heavy oils, which will contaminate the next cargo. Rust will, above all, render tank cleaning much more difficult, cause delays and perhaps cargo claims.
Due to the above reasons steel is practically never used in chemical tankers without a protective coating . Coating techniques have advanced greatly in latter years. Still, however, one does not dare to use coatings for products, which are really aggressive to steel, e g acids (such as phosphoric acid). One has to reckon with coating defects where corrosion will start. One exception to this is rubber linings, which have been in use a long time with corrosive cargoes.
Generally speaking, steel is resistant to alkalies, even in high concentrations (caustic soda, ammonia).
Properties & composition of stainless steel as shipbuilding materials for chemical tankers
Use of magnesium and alluminium alloys as sacrificial anodes
Cuprous alloys for shipbuilding of seagoing chemical tankers
Physical properties & maintenance requirements for various tank coatings
Introducing PTFE (polytetrafluor ethylene) as Gaskets and packing onboard chemical tankers
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