WEAR AND TEXTURE ANALYSIS OF MARINE HULL COATING SYSTEMS
- Marine fouling increases operator costs – fuel consumption, dry dock time, lost revenue
- TBT ban – increasing legislation on Cu biocides – requirement for novel coating systems
- Development and optimisation of coating solutions requires many formulations based on intended marine application – static fouling exposure to high speed operation
- How to characterise loss rate and texture evolution of hundreds of formulations at R&D stage?
- XYris 5000 Surface Profiling system – high throughput, automated, nanometre resolution measurement of coating wear loss rate and surface texture
Biological hull fouling presents multiple problems for a vessel operator. Increased drag impacts fuel economy, emission of CO2, NOx and SOx. Mechanical engine loading is increased to maintain speed while severe fouling impacts vessel manoeuvrability. The fouling itself presents an additional layer requiring removal during maintenance, painting and inspection cycles, increasing dry-dock immobilisation time, maintenance costs and lost revenue.
High performance and low cost of tributyltin (TBT) based coating solutions were widely adopted prior to linkage to the collapse of marine ecosystems, and their subsequent ban. The use of current copper based solutions are increasingly subject to legislation. This has forced a demand for alternative technologies offering anti-fouling and hull preservation capability.
The formulation of a coating product depends strongly on the target application. The performance balance may vary considerably depending on operation parameters, such as vessel velocity, where it is apparent that very different requirements will arise from static exposure conditions to those encountered in high speed trading. During product development many compositions are tested to determine the optimum balance of performances.
In-service endurance and drag performance of coating systems are quantifiable through the measurement of the rate of coating loss and hull surface roughness testing. Where total coating thicknesses are characterised by micro-meters, and loss rates by nanometres per day, the use of precision measurement systems to track the coating loss and surface texture evolution becomes critical in characterising coating performance.
The TaiCaan XYris 5000 Series has been developed for rapid and automated analysis of coating wear rate and texture evolution at the nanometre scale. Throughputs of hundreds of samples an hour are achieved, with flexible software tools to automate the acquisition, storage and processing of measurement data. Customisable reporting tools prepare at-a-glance performance comparison of coating formulations over lifetime testing, accurately and repeatably evaluating your coating solutions.
A measurement coupon is prepared as an inert substrate disk, or cylinder, designed to be rotated at a constant angular velocity. In the case of the disks the coating may be applied in radial stripes, with the radial distance equating to a particular hull speed. For the cylinder approach, the coating is applied to the outer surface then rotated within a second concentric cylinder, under water, to achieve a viscous shear between the cylinder walls, equating to hull speed under investigation.
At predetermined intervals, the coupons are removed from the test and introduced to the XYris instrument. They are mounted on a spindle and rotated under a confocal laser displacement meter, such that the height of the coating and the substrate are measured as a ring. Secondly, the coating regions are measured over an area to record a full 3D surface measurement. The operator may select a predetermined programmed sequence for ring (height) and area (surface texture) measurement, or program new sequences as required using an intuitive user interface.
The data is then automatically processed and stored for required parameters such as the coating thickness and surface finish from a wide selection of industry standards (DIN, ISO, JIS, ASME, etc).