MARINELINE® & CHEMLINE® COATINGS FOR INDUSTRY

APC Independent Tests - Part 3

An Independent Technical Report on the Suitability of MarineLine® for Cargo Tank Coatings - By Anticorrosion Service - del dott. Norbert Ackermann

COMPARISONS & CONCLUSIONS

COMPARISON OF MARINELINE WITH OTHER TANK COATINGS

MARINELINE, if compared to other available tank coatings such as epoxies, epoxy phenolics, epoxy isocyanates or zinc silicates offers several advantages, especially in the case of chemical carriers.

Unlimited cargo range. All common cargoes can be carried without limitations, the only restriction being the tank equipment material (pumps, pipes, valves etc.). All other available tank coatings have a limited cargo range. For instance, organic coatings are unsuitable for aggressive cargoes such as phenols, amines, methylene chloride and most acids. Zinc silicates are suitable for strong solvents but have limited pH tolerance (pH 6 - 9.5).

Easier cargo handling. Organic coatings are subject to absorb a certain percentage of strong solvents and therefore must be given time to dry out and recover after an aggressive cargo. If the carried solvent is water soluble, complete drying before water washing or carriage of watery cargoes is mandatory. Zinc silicate coatings have a porous structure, which can make cleaning after some cargoes very difficult, and zinc salts may contaminate cargoes such as aviation fuels or foodstuffs. These restrictions result in loss of cargo time and limitations for cleaning operations. MARINELINE, as stated by the manufacturer and verified by the above mentioned immersion tests, has very low absorbtion values posing no limitations to cargo sequences and making tank cleaning easier.

Duration of the tank coating. The duration of an organic tank coating depends on service conditions. If aggressive cargoes are carried frequently, the coating film ages and weakens earlier due to continuous solvent absorption/evaporation, shortening the service life.

However, given the low cargo absorption of the coating film, the useful service time could be significantly longer than for organic coatings.

A possible disadvantage of MARINELINE is the necessity to heat cure touch-up spots. Notwithstanding the good mechanical resistance of MARINELINE, mechanical damages may occur and must be repaired, requiring the availability of a heating device on board.

Comparison of MARINELINE with Stainless Steel

Tanks coated with MARINELINE have a broader cargo range than stainless steel tanks, since, for instance, halogenated compounds are not recommended for stainless steel. Another example is sulfuric acid, which is suitable for stainless steel at concentrations over 90%, but becomes corrosive to stainless steel at lower concentrations, posing some problems when, after discharging, the tanks have to be water washed. The range of cargoes carried in tanks coated with MARINELINE is limited only by the cargo equipment, which is usually made of stainless steel and hence restricts the suitable cargoes. MARINELINE coatings offer a very significant economical advantage, if compared to stainless steel, allowing at least the same cargo suitability at a much lower cost.

However, it must be pointed out that in the case of acid carriage, coated tanks run a higher risk. If undetected mechanical damages occur, damaged spots may suffer severe corrosion with possible perforation of tank plates. Notwithstanding the good mechanical resistance of the coating, accidental mechanical damages may always occur. For this reason, in the case of chemical carriers dedicated to acid transportation, stainless steel tanks should be preferred. For all other cargoes, MARINELINE is economically more convenient than stainless steel. MARINELINE is also suitable for occasional acid transportation, provided the tanks are inspected for possible damage spots before loading and after unloading.

CONCLUSIONS

MARINELINE is a 2 component coating with good application properties, which can be applied following regular tank coating procedures, the only additional requirements being heat curing and a final spark test (holiday detector test). The heat curing can be carried out with hot air in a reasonably short time (12 hrs at 71° or 4 hrs at 93° C).

According to the chemical resistance tests carried out, MARINELINE coatings comply with the resistance list provided by the manufacturer, the only exception being the colour change in strong acid immersion. Although only a limited number of tests were performed, the suitability to these few, very aggressive chemicals indicates a superior chemical resistance and very low absorption rates, unparalleled by traditional tank coatings.

For chemical carriers of all IMO classes MARINELINE, owing to its unlimited cargo range as well as owing to easier cargo handling and tank cleaning, offers significant advantages over traditional coatings.

For product carriers, especially if the carriage is limited to "white oil products", traditional tank coatings may be economically more convenient.

If compared to stainless steel tanks, MARINELINE offers the same cargo range (limited only by the equipment material) at a much lower cost. However, in the case of dedicated acid carriers, stainless steel tanks should be considered a safer choice.

Anticorrosion Service
del ar. Norbert Ackermann

 

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