To indicate the advantages of using coated steel tanks instead of stainless tanks in the construction of chemical tankers, Ohio-based Advanced Polymer Coatings (APC), has published the findings from its own comparative study between the two different types chemical tanker. APC is also the developer of the Siloxirane based anti-corrosion system MarineLine.

The newbuilding cost of a 37,000 dwt. double-hulled chemical tanker with stainless steel tanks is almost exactly twice that of the same vessel equipped with MarineLine protected carbon steel tanks.

The study suggests that with amortization of the financing cost, including an assumed interest of 6% over 20 years, the $75m stainless steel tank newbuilding would represent a per-day amortization cost of $23,433. This compares with only $11,810 per day for the MarineLine-treated alternative with its capital cost of $37.8m.

In order to generate sufficient income to cover the respective amortization costs, there would need to be a substantial difference in the freight rates charged. According to the APC case study of a 29,000 dwt tanker carrying methanol and charging $20,000 per day, this resulted in a rate of ¢69 per dwt/day being achieved by the owner. The survey estimates that an equivalent stainless steel tank vessel would have to charge a rate of $1.09 per dwt/day to produce the same operating margin, an increase of over 58%.

The 37,000 dwt chemical tanker newbuilding option involves identical operating costs of $6,162/day for both the stainless steel and MarineLine-protected vessels. With the addition of the respective amortization costs and employing the same ¢69/dwt/day factor (which generates a revenue of $25,530 daily) the owner or operator of a stainless steel tank vessel would be faced with anoperating deficit of $4,065 a day.

By contrast, the survey suggests a MarineLine-coated counterpart would be notching up a daily gross profit of $7,558, enabling the vessel-financing costs to be paid off in just nine years.

As well as the newbuilding market advantages, the survey goes on to suggest that similar operational bonuses are possible when the coating is applied to in-service vessels. The all-inclusive initial outlay for the MarineLine, anti-corrosion treatment of a 46,000 dwt products/oil carrier involving a surface area of 30,000 m2, is marginally more expensive than a phenolic epoxy coating system. However, the resulting vessel upgrading would enable this additional cost (estimated to be in the region of $.25m) to be recouped within four months through improved vessel utilisation factors.

These improvements result from enhanced surface smoothness (0.7RA) and the non-absorption features of MarineLine, as well as the treated tanks' ability to handle a greatly extended range of chemical and other liquid cargoes.