MarineLine® E-Newsletters

Profitable Tanker News about Marine Cargo Tank Coatings
Issue 20
1 in a 2-part series on Heat Curing
WHY a Fully Cured Cargo Tank Coating Matters For Long Term Performance

Monitoring temperature during heat curingTo adequately protect coated cargo tanks of chemical and product tankers, the lining must be cured. For the MarineLine® system, this means a ‘Forced Hot Air Heat Cure’, which is the final step in the entire application process. MarineLine® takes the heat curing process very seriously, and is regarded as the Gold Standard in the industry. This final heat curing step is what enhances and accelerates MarineLine®’s patented polymers to highly crosslink together, forming a tightly knit, nearly impenetrable structure.

MarineLine® Believes a Cured Coating is Critical

The MarineLine® application process begins with proper surface preparation of the substrate, followed by careful application and inspection of the coating at each stage. Final curing of the coating while the ship is still at the yard provides the maximum level of corrosion protection for the steel tank, ensuring long term performance, and protecting chemicals carried at a high purity level.

Shipowners specify the MarineLine® coating system because they know when a ship leaves the shipyard, it is immediately ready for service, able to safely carry thousands of chemicals and liquids approved by the IMO, including aggressive cargoes and other profitable cargoes. There is no waiting time for additional curing, or the need to carry hot cargoes for post curing.

APC’s unique heat curing system for MarineLine® has been built up over many years through continual investment to acquire necessary infrastructure and heat curing equipment and to develop stringent operating procedures, and to extensively train its operators. Note heat tubes (far right) that carry hot air to cure the MarineLine® cargo tank coating.

Heat tubes carry hot air to cure coating.

Other Coatings Companies Take a Different Approach

Some coatings companies that offer phenolic epoxy or bimodal epoxy tank linings state a “post cure is mandatory prior to carriage of any cargoes.” However, while they cite various ways to possibly achieve a post cure, none of these methods are under their control, with all responsibility forced upon the shipowner to perform the post cure and carefully document all steps.

Note that other coating companies insist as a “condition of service” that the shipowner guarantee that records be maintained at specified temperature and time requirements at all times during post curing. So if tank coating problem arises in the future, the shipowner must take the blame if the post curing was not done perfectly or not diligently recorded fully. This is a great risk to the shipowner that could present a large future liability.

So unlike the MarineLine® system with its turnkey approach, when shipowners ask other coatings companies how they need to post cure their tank linings, they offer various methods. Here is a sampling:

A. forced hot air heat cure (just like APC/MarineLine® recommends in the shipyard)
B. carry a full hot cargo as specified
C. immerse (fill to maximum capacity) the cargo tank with hot seawater/freshwater for a specified time and temperature
D. carry non-aggressive cargoes for three months as specified
E. apply a hot recirculating wash with seawater/freshwater using tank cleaning machines (butterworthing) for a specified time and temperature.

NOTE: Published independent studies show that ‘D’ and ‘E’ do not fully cure these systems. For complete post cure information on any cargo tank coatings, check directly with the coatings manufacturer.

Again, proper post curing with any of these methods is the full responsibility of the shipowner, so before those cargo tanks can be put into full service, the shipowner will have to incur large heating fuel expenses to heat the water needed for butterworthing or immersion, or other methods, further reducing profitability. As one coating company states, “It should be noted that failure to observe the specified curing conditions prior to cargo immersion may have a permanent adverse affect on the resistance properties of the coating.”

Problems Emerge by Not Fully Curing Coatings

Some coating companies are promoting that they are ‘equal’ to MarineLine®.’ This cannot be true, as MarineLine® is based on a unique patented polymer system with the highest resistance capability of any cargo tank on the market, with the industry’s best heat curing system. In fact, if a competitor’s tank coating does not achieve a full cure, problems can arise. Reports from inspectors and surveyors of competitor’s cargo tank coatings show that ships are being taken out of service for various issue including cracking, and are being recoated, even after just a short service life and carrying easy cargoes. Many times the problem is the post cure, which again, is forced upon the shipowner to assume all responsibility. FOSFA even has a stipulation in its operating procedures that says coated cargo tanks must be fully cured prior to any carriage.

Cracks and blisters

APC/MarineLine® takes the opposite approach and looks to form an ongoing partnership with its customers, along with turnkey responsibility for the final curing of the coating. APC believes in fully taking care of the customer at every stage.

For more information on how MarineLine® coating can help your tanker operations, contact your MarineLine representative.

In the next issue of Profitable Tanker, APC will examine the various steps in the MarineLine® Heat Curing process to provide a glimpse into this professional work.