THREE 90m-diameter crude storage tanks, at Repsol's Cores project in Cartagena, Spain, have been protected internally with Jotun Paints' 'Tankguard Storage' phenolic epoxy coating, and externally with a Jotun epoxy system finished with polyurethane topcoat.
The contractor employed automatic dust-free blasting within the tanks, which enabled the internal coating system to be completed in only eight days, representing a time saving of some 20 per cent.
The paint specification for the tank internals called for blasting to Sa2.5, followed by two coats of 'Tankguard Storage'. The internal area to be coated consisted of the bottom of the tank plus the bottom two metres of the tank wall, giving a total area for the three tanks of approximately 20,000 sq m.
'Tankguard Storage' is a high solids phenolic-resin coating, which is ideal for corrosion resistance to a wide range of chemicals including crude oil, together with aromatic and aliphatic solvents. It also has very good water resistance.
The objective of the contractor's use of dust-free blasting was to make the coating of the tank floor an easier and cleaner task. Throughout the blasting and coating application, the tanks were also dehumidified. Maximum and minimum air temperature requirements were 21 deg C and 9 deg C respectively; a temperature of 16 deg C was maintained for most of the period with a relative humidity of less than 30 per cent.
As a result of the closely-controlled application conditions, no holding primer was required and the protective system comprised two 200-micron coats of Jotun's 'Tankguard Storage'; stripe coating of welds, corners and other problem areas was carried out before each full coat. This use of a two-coat system resulted in substantial benefits that included not only the saving of the cost of the primer but also much-reduced application time.
Following application and curing, spark inspection showed that the work was entirely satisfactory, with no repairs being required.
For the external protection, the specification called for blasting to Sa2.5 followed by a coating system consisting of one 60-micron coat of Jotun's 'Barrier' zinc-rich epoxy primer, one 130-micron coat of 'Penguard Mio', an epoxy formulation pigmented with micaceous iron oxide, and an 80-micron coat of 'Pur Une' polyurethane topcoat.
The total area treated was 41,000 sq m, and comprised the top and external sides of the tank plus the topmost one metre of the tank wall internally. As with the internal coating, inspection showed the work to be completely satisfactory.
