Parkol Marine Engineering, based in Whitby, UK has recently applied a thermal sprayed zinc coating to a new whitefish trawler, the ‘Resilient LK195’, to protect it from corrosion.
At the same time as the Resilient was being coated, the 26m single rig whitefish trawler, the Guardian Angell LK272, was back at the Whitby boatyard for a refurbishment. The effectiveness of the zinc coating process can clearly be seen to the rear of the Guardian Angel where the trawl doors are brought back on board. Despite extensive paint damage, Metallisation points out that the robust thermal sprayed zinc base layer clearly remains and continues to protect the hull from rust.
The anti-corrosive properties of the metal spraying process are widely recognised in the shipping and marine industry, where steel super structures and vessels are subjected to very damaging corrosion from the sea and salt laden air of the world’s shipping and fishing industries.
Fishing boat builder Parkol opted for the Metallisation ARC150 system and a 20 metre supplies pack, which makes the system very flexible, enabling the engineer to move easily around the boat and gain access to all spray areas. Metallisation also supplied an extension trolley that included another 20m supplies pack, this ensures the energiser can be kept well away from the spray area. Due to the nature of the project, Parkol engineers used MIG reels to spray from, as they are much easier to move around and load compared to drums. In the last twelve months they have sprayed over one tonne of zinc on to trawlers of all shapes and sizes.
Prior to zinc coating and painting of trawlers, the surface is grit blasted to SA2.5 cleanliness and a profile of around 75 microns. Within four hours the zinc coating is then applied which instantly cures. Finally, the zinc is then sealed and finished with several coats of marine grade paint.
The Metallisation ARC150 arcspray system has been designed for high-throughput coatings. At 500A. It can apply up to 52kg/hour of zinc or 12kg/hour of aluminium. This high capacity, combined with the flexibility of the system makes it ideal for coating large areas such as boat hulls, offshore oil platforms and other large steel fabrications. The spray rate and pistol are easy to control, also making it suitable for spraying more intricate areas like deck rails and hardware. The coating finish is very fine, which creates an ideal base for the final paint top coats.
In the Arcspray process, two electrically charged wires are driven and guided so that they converge at a point and form an arc. An air nozzle atomises the molten metal produced from the wire and projects it towards the work piece using high pressure air. This spray solidifies when it hits the surface of the work piece to form a dense coating, which protects against corrosion. The driving of the wires is typically either by air motor or electric motor and gearbox arrangement.
By Jake Frith