The advance of graphene coating additives has taken another step forward. Large-scale commercial trials are now underway on two commercial ship hulls using a new graphene additive mixed into their bare-metal primer.
Perth-based Talga, producers of battery anodes and graphene, have applied their Talcoat graphene additive to the hulls of the Arica and Algarrobo container ships both sailing South American routes. The 33,000GT Algarrobo has a 700m2 section that has been painted using the new product.
The advanced trials are testing functionalised graphene as a performance booster for existing commercial marine coatings, and are hoped to demonstrate graphene’s exceptional mechanical properties when added to standard coating systems.
Over the coming 12-18 months the Talcoat-coated test areas will be evaluated in the harsh real life conditions of global cargo shipping. Talga expect to show a range of environmental and economic benefits, including improved corrosion resistance, decreased metallic paint loss into oceanic ecosystems and better productivity through lengthened drydocking cycles.
“The maritime coating sector is a very large market and well suited to use of our graphene additives for improved environmental and economic outcomes,” explains Talga’s Managing Director, Mark Thompson. “Additionally, by successfully taking this new product from the laboratory to commercial-scale application on a 33,000 tonne ship, which is being tested across global marine environments, we are showcasing our graphene’s real-world potential as a bulk industrial product.”
The core of the Talcoat system is an on-site dispersible powder that can be added to cans of regular coatings on demand and on-site.
Whilst the first test involved Talcoat additive being mixed into Akzo Nobel’s Intershield 300 (a two-part epoxy) before dispatch to the ship management company for application, the second of the two trial applications, to the Arica, was mixed on-site. Talcoat and another regular two-part epoxy were supplied separately and mixed at the drydock by the paint applicators before spray application to the vessel during drydocking.
This is a significant commercial development as graphene based products commonly require factory conditions or liquid dispersions to work.
In both cases, the mixing and application successfully met all conditions and standards required for the vessels’ class.
“The respective onsite commercial applicators reported successful applications, with the additive having insignificant or no adverse effect in terms of application and curing, at both trials,” states Thompson.
“The Talcoat graphene additive performance in each trial will be monitored over the vessels’ next 12-18 months of service, with the results expected to demonstrate a range of benefits, including greater adhesion to the substrate and adhesion to subsequent coating systems, as well as improved corrosion protection.
“Improvement in abrasion resistance is another advantage expected based on lab-scale mechanical performance tests undertaken prior to the trials, whilst other benefits such as the potential of reduced coating thickness remain to be further investigated.”
Talga’s preparation for marine application included multi-stage testing to optimise both graphene loadings and Talga’s dispersion technology for epoxy based commercial primers.
This testing included an industry-accepted ASTM prescribed Salt Fog Test (ASTM B117), where steel panels coated with the Talcoat-boosted primer showed improved corrosion protection performance compared to current ‘state of the art’ commercial systems.
Since the hulls will be exposed to considerable abrasion and mechanical damage during service, mechanical performance tests were also carried out to ASTM standard by The Welding Institute in the UK. The results showed a significant improvement in primer performance, including greater adhesion to the substrate (by ~7%), greater interlayer adhesion to the subsequent (antifouling) coating systems (by ~14%), and consistent improvement in abrasion resistance.
The test areas along the ship’s starboard side, both above and below the water line in contact-wear sites, were blast cleaned to remove prior paint systems before the Talcoat-enhanced primer coating was applied, next to a reference area without Talcoat. Application was in two coats, using manual spray systems. No adverse effects were noted in terms of stability in resin, application, curing and surface features. The test areas were then over-coated with the standard topcoats used on the rest of the vessel.