Hull protection using chlorinated rubber paint
WITH our liveaboard narrowboat being more static than mobile, we had decided on a two to three years blacking cycle. However, we found ourselves in a bit of a quandary by way of hull protection choice because after being built in 2005 she’d always been blacked using chlorinated rubber, rather than the more traditional bitumen.
We’d purchased her during late October 2015 and at time of purchase she was in dry dock in Lymm, Cheshire. The hull survey indicated she’d been taken out of the water on a regular two-year cycle for her hull to be thoroughly checked. The last application of chlorinated rubber paint before we bought her took place in April 2015.
As new arrivals in the UK at the time of purchase, we knew nothing about narrowboats and one aspect that had us somewhat confused was hull blacking. We’d also read and heard bitumen was the preferred and, seemingly, the most commonly used hull protection. We understood too, that it was important to have it done every two to three years.
The sole owner of the boat explained to us why he’d used chlorinated rubber paint, his main reason being that it afforded better anti- rust protection to the hull than bitumen and was longer lasting in the face of abrasion. It also had good intercoat adhesion, was flexible and ideal for maintenance purposes.
The boat’s construction commenced in late 2003 and was completed in October 2005. Interestingly too, the owner also informed us he hadn’t used anodes on the hull, aside from originally fitting some to the swim at time of construction. His reasons for not refitting anodes were that for them to function correctly in their limited purpose, they’d have to be placed in line of sight and close together, which meant a fair number of anodes were needed on the 60ft hull.
Equally important, for anodes to be effective they have to rely on good contact with the steel plate. If applied over protected surfaces their limited performance would be even less.
In the pre-sale hull survey, it was noted the state of the hull without anodes hadn’t affected overall condition. There was also no evidence of stray current corrosion such as active galvanic or electrylic corrosion, and although a galvanic isolator doesn’t replace sacrificial anodes, she was fitted with one.
Two and a half years on from purchase, Ashbridge, as she was known, underwent a DIY external makeover and name change to Sabi Star (more in keeping with our Zimbabwean heritage). This translated to a much-needed change of livery from maroon to cream and navy blue.
By this time too, we were more or less marina based and because of our relatively static existence, we began to worry about hull maintenance, so decided Sabi Star needed to come out of the water and have her hull checked. It’d been two years and eight months since we’d bought the boat and three years-plus since her last hull blacking.
I managed to get an almost immediate booking at Devizes Marina Boatyard and when Brenda and I discussed blacking options, we decided to stay with chlorinated rubber paint. Whenever I’d checked our boat’s waterline, there was no indication of rust and that too gave me reason to stay with the product.
A few days before dry docking a handful of marina friends kindly helped me up the rather daunting 29-lock Caen Hill Flight and thereafter, I took Sabi Star into the boatyard where she was taken out of the water.
Devizes Marina Boatyard did a thorough job, and after the hull was scraped it was pressurehosed, and then wire brushed. All of us were pleasantly surprised at the end of the exercise to see the hull was still black. Granted, there was some stray current corrosion but very, very little.
Seemingly too, in some quarters slight confusion reigned regards the use of chlorinated rubber paint. We’d heard it was to be banned from January 2019, however, the suppliers of the paint informed me it certainly didn’t apply to their product. Further research showed it was coal tar products that are to be banned.
For the application of two coats of chlorinated rubber paint we used 16 litres, and as an additional protective measure had six anodes fitted. Back on the water, we were able to relax in the knowledge that chlorinated rubber paint certainly has its merits, and at £10 more than five litres of bitumen it’s an affordable alternative option.