The new black
If you thought it was all coal tar, think again
In the old days, when it came to hull painting it was, indeed, largely a case of ‘black is black’. You put your boat in dry dock every couple of years, pressure washed it and re-blacked it – and the only decision was whether to use coal tar solution or bituminous paint. And to a certain extent, that decision was made for you by what type of paint had been used previously.
Not any more. There are a whole range of different coatings available, with different qualities and different prices to match. There’s still basic ‘standard black’ – the successor to coal tar solution – for a ‘cheap and cheerful’ re-blacking lasting two or three years. But there are several higher- quality, longer-lasting products available now.
Higher performance bitumen products are available that last better than traditional black bituminous paint. They include paints which have more resistance to oil and diesel (a problem with traditional bituminous), build up a thicker layer (‘bodied’ bituminous paints) or provide a harder gloss finish.
Vinyl tar coatings are also on offer today, which have the oil and diesel resistance of standard black, but are harder wearing, more flexible, durable and weather resistant.
Both of these types of product may dry to a less shiny black finish than the traditional ones, but you can always overcoat them if the finish is important to you.
These more advanced products can extend the intervals between the expense (and for DIY-ers like myself, the not terribly pleasant experience of spending a week in the bottom of a dry
dock) from two or three years to perhaps four or five years. But can we do better than that?
Canal Boat recently visited a couple of companies who’ve been developing more specialist treatments, mainly based on two-pack epoxy systems, and who believe that the answer is ‘yes’.
The first of these was Napton-based boatbuilders Bluewater Boats. They’ve been advocates of advanced two-pack epoxy paints for many years. But they’re the first to admit that it’s a more expensive alternative, particularly as it requires grit-blasting the hull first.
And we’re not just talking about taking old paint off here: Bluewater are mainly concerned with brand new boats, but even new steel is covered in tiny fragments of ‘millscale’ from the manufacturing process. It all has to be blasted off before the painting starts: Bluewater told us that even grade A steel may well be hiding 0.5mm deep pits under the millscale.
As for the paint itself: Bluewater use a high-build epoxy, building it up to a total thickness of 400 microns. All paint is permeable to a certain extent, but at that thickness, say Bluewater, the water really won’t get through. That’s a lot of paint, and it’s expensive stuff – it could add up to a couple of thousand in paint costs alone. However, they believe it’s worth it when you’re spending £100,000 or more on a new boat.
And is it? Up to now it’s been difficult to tell, as two-pack epoxy paints haven’t been used on narrowboats for long enough to really judge how long they last. Recently, though, came ‘the proof of the pudding’. The owners of narrowboat
Ariadne (the subject of our boat test in the May 2011 CanalBoat) brought their boat back to Bluewater for a check-up – and the good news is that the hull is still basically pristine after five years. Even where there’s damage (and unfortunately
Ariadne suffered a bad scratch a year earlier) there’s been no ‘creep’ at all: where a hull painted with a normal coating would have seen rust spreading to the area around the damage, here it’s still limited to the actual scratch itself.
That’s not the only example. Bluewater say they’ve recently looked at an 11-year- old boat and it’s still in excellent condition. They guarantee their coatings for seven years, but they say that the same paint is used on oil rigs, where it lasts for 15 plus years.
Another company we’ve visited is Debdale Wharf near Foxton. While Bluewater are mainly about treating new hulls, Debdale have developed a specialist treatment aimed more at
‘These advanced products can extend the intervals from two or three years to perhaps four or five. But can we do better than that?’
‘Zinc coating doesn’t come cheap. But, having started offering the treatment two years ago, already over 80 boaters have felt it worthwhile’
re-blacking older boats including historic craft. They, too, use two-pack epoxy paints, but it’s what they do first that’s their speciality.
Debdale believe they’re the only boatyard in the country to offer a zinc-coating process for narrowboats. A dedicated bay has been created for blasting and coating: lined in rubber and steel, with specialist extraction plant, plus shrouding and suction kit to stop any grit from getting inside the cabin.
Here, the boats are grit-blasted and then coated using a spray-gun which uses a powerful electric current to melt the zinc before applying it to the hull. Once the zinccoating is complete, the hull is painted with two-pack epoxy.
Again, it doesn’t come cheap. A typical cost is around £4,500 inc vat – but having started offering the treatment two years ago, already over 80 boat owners have felt it worthwhile. How long does it last? It’s difficult to tell for sure as yet, but Debdale say that with just the Hempel 2-pack it would be ten years plus; so with the zinc, it’s much more – quite possibly, they reckon, indefinitely. Even in the harsher environment of salt water, similar treatments last ten years. Their first boat came out of the water recently with “not a mark” – and they say boat owners can call them after 4-5 years for a free lift- out and checkup, or any time if they’ve been in an accident.
So, to sum up: there are some interesting advanced treatments available these days that offer hull protection going a long way beyond the traditional three coats of coal tar solution. They’re not cheap – but given the much less frequent intervals needed for repainting, you might like to think about whether they’re worth it.
I’ll certainly be thinking about it, next time I’m in the bottom of a chilly dry dock with a brush in my hand, painting the seemingly vast area of the boat’s bottom and realising I’ll be doing it all again in just a few years…
Anything that extends the intervals between doing this has to be good news!
Bluewater boat still looks good after five years
Bluewater use the same treatment for tanks
The extraction plant installed at Debdale
Debdale’s treatment on a historic boat hull