Marine cargo tank coatings for chemical and product tankers
Zinc silicate, novolac phenolic epoxy and siloxirane linings, what each carries, what attacks it, and why the cargo resistance list is contractual rather than regulatory.
A cargo tank coating decides which cargoes a carbon steel tank can carry, and the decision is commercial rather than statutory. IBC Code chapter 6 requires materials of construction and linings resistant to the cargo, and the ship’s Certificate of Fitness product list constrains what may be carried, but nothing in the Code names a coating type, a grade or a film thickness. What governs in practice is the coating manufacturer’s cargo resistance list, which is a contractual document.
Three families dominate. Inorganic zinc silicate suits aromatic hydrocarbons, alcohols and ketones, and is attacked by acids and alkalis including sea water; it is not suited to vegetable oils or animal fats, and its metallic zinc pick-up risk rules it out for foodstuffs and aviation fuels. Novolac phenolic epoxy covers a wider acid and alkali range, is applied in two or three coats and on some products requires a heat post-cure, but its resistance to amines is very limited. Siloxirane coatings are marketed for acids, alkalis and solvents together and leave the yard fully cured.
The practitioner term for the behaviour that complicates cargo sequencing is coating memory: an organic lining absorbs cargo and releases it slowly, which limits back-hauling and makes a wall wash result on a coated tank harder to interpret than one on bare stainless steel. The full article will cover each family, the resistance list practice, the post-cure requirement and the comparison against bare duplex stainless tanks.