Nauteco

Modern Paint Systems for Inland Waterways

Bitumen versus Epoxy Primer and Antifouling – a real life lesson

Canal boat builders, fitters and owners have long used bitumen-based paints for protecting and waterproofing steel hulls, the tradition dating back over 7,000 years to when tribes in Mesopotamia used naturally welling pitch for caulking their reed boats. Yet canal enthusiasts Frank Smith and Alan Hedges, both members of the Latham Marine Cruising Association in Lancashire, have good reason to say that the old ways are not necessarily the best.
Like a present day parable, Frank and Alan both own 50ft steel canal boats of the same make and age, although each decided to protect the hull in a different fashion. In 1997, after consulting Nauteco’s manufacturing partner, Frank used an epoxy primer to safeguard the steel and inhibit corrosion, overcoating this with the firm’s Performance Antifouling; whilst in 1999, Alan decided upon traditional bitumen to reduce effort and cut costs. Two years on, Alan’s hull was already showing signs of corrosion and damage, whereas Frank’s was still as good as new and significantly easier to clean. The moral? What you save on paint initially, you lose on dry-docking charges, more frequent maintenance, extra work and all-round frustration.

Actually, says Nauteco’s marine specialist, this is a classic example of modern surface coatings technology improving upon a time-honoured material, albeit one that had virtually no rival for thousands of years. A bi-product of the second distillation of crude oil, bitumen is well suited to this application because of its water resistance, flexibility and adhesive properties. However, the specifications of bitumen coatings can be quite varied, which has an effect on the properties of the material, and once they are damaged, so that bare steel is exposed, do not have any integral anti- corrosive properties.

As Alan found to his cost, once corrosion takes hold, rust scabs can develop beneath the bitumen film, thus bypassing the waterproof protection of the coating. Moreover, as Thor Hyerdahl discovered when planning the Tigris Expedition, bitumen sometimes lasts no more than a year before cracking and letting in water. When consulted by Frank, Nauteco’s paint technicians instead recommended two base coats of epoxy primer, having first removed any contamination on the hull by high pressure washing or shot blasting, according to condition. Nauteco’s Two Pack Epoxy Primer is a high performance, 2-pack product specifically designed for protecting steel in tough environments, such as encountered on canal boats, and it combines high adhesion, water and chemical resistance with outstanding anti-corrosion properties. It can be applied by brush, roller or spray, then lightly abraded once dry to provide a key for the topcoat.

To prevent the build-up of unsightly weed and slime that would otherwise reduce cruising speed and fuel efficiency, the Nauteco team recommended overcoating the primer with its innovative Performance Antifouling which is considered the most eco-friendly of its kind, as it works without releasing highly toxic biocides. Once the coating is immersed in water, a catalytic reaction is triggered, which causes it to develop a smooth, slippery microfilm that sheds marine growth and reduces the presence of potentially damaging anaerobic bacteria. Proved across the oceans of the world and coastal waters on all continents, the product is now proving equally successful on inland waterways.

Certainly, Frank will testify to the success of the Two-Pack Epoxy Primer and Performance Antifouling combination, so too does Alan, who has now treated his boat in exactly the same way, with other club members planning to do so too.