What is "Tar" for a boat owner?

[AntarcticPilot]

I'd like to see a citation for that, particularly since coal tar ointment (as I posted above) is still on the WHO list of essential medicines. Are they really recommending a carcinogen as essential?

I guess that it is used for its antiseptic properties. I'm also fairly sure that the carcinogens aren't absorbed through the skin, so it's OK for external use. I hope so - when working for CTRA I got an unreasonable amount of tar on my hands! But I also suspect that it isn't raw coal tar that is used, but rather phenols derived from coal tar.

 

[pcatterall]

I recal when coal tar was bannned as a road surfacing.It was widly used and I dont recal being made aware of any handling issues.
nowadays when a road is being rebuilt it has either got to be removed to contaminated land sites or it can be treated. Treating is now proving a cost effective method on some sites.
I aso recal in the 1940s that we used to pick out the gas tar between street 'sets' and make model figures ( gas tar babies!) .... still going strong despite this...cough cough!!

 

[Quandary]

Long ago, before most of you were born, Primocon keel primer was bitumen based, this gave good rust protection to the iron but always bled through lighter coloured antifouling paints leaving unsightly big brown stains on the surface.
I still believe in the protective qualities of bitumen paint, about ten years ago I built a garage for two cars with an attic loft over for the storage of sails, large tools, bikes, outboards etc. The floor is supported by a 6.6m. long central steel beam 305mm. deep, when the steel was delivered I gave it a coat of bitumen paint, with another coat once I had rocked* it up into position, there is stil no sign of rust. The outside access staircase is supported by timber columns set into steel shoes at ground level, the shoes were similarly painted and despite contact with the ground have not begun to rust so I think the stuff is effective. I used a lot of it earlier when involved in refurbishing this house.
It is cheap, available in various size tins down to 2.5 litres from Johnstone Paints and many others but you only use it where you are happy with a gloss black finish, it is not suitable for overcoating.

*Btw. if you ever need to lift a long heavy steel beam 2.5m single handed it is easy using your concrete blocks to raise two temporary columns at about 40% and 60% of the total length, positioned so that at the right height the ends can be rotated onto the padstones.

 

[Ship'sCat]

Having started the thread I must say that the comments so far are very interesting and informative and I thank everyone.
At the moment I am minded to re-use the existing keel bolts, depending on how the other samples show - hopefully I can take some more out this weekend. In the meantime I don't want to acquire 5 litre tins of stuff with lots of health and environment warnings and might look for a modern sealant or maybe the Stockholm tar.

 

[alan_d]

... I'm also fairly sure that the carcinogens aren't absorbed through the skin, so it's OK for external use. I hope so - when working for CTRA I got an unreasonable amount of tar on my hands! ....

Wrong, I'm afraid. Many decades ago my mother worked in occupational health for a Gas Board, and one of her jobs was to look out for "pitch warts". A pitch wart or hydrocarbon keratosis is a type of skin reaction to several chemicals that cause epidermal hyperplasia, which may be associated with tumor or cancer formation. Certain petroleum intermediates and products, retorted shale oil, coal liquification intermediates, a number of coal tar derivatives and arsenic can stimulate the epidermal cells to produce these effects. See, for example, http://www.hse.gov.uk/pubns/indg435.pdf

 

[BobnLesley]

...Coal tar comes in two types that also have different properties - high temperature tar, which results from the production of old fashioned town gas...Ohlin Karcher's view of the safety of tar is seen through very rose coloured glasses. Coal tars, both the old-fashioned stuff from the gas works that resulted from high temperature distillation of coal and the low temperature stuff that results from the production of smokeless fuels and is what is available these days, are chock full of aromatic carbon compounds including phenols and many others, a large number of which are carcinogenic or biocides (=poisons!)...

That makes more sense. I was surprised by OK's comment having many years ago been involved with managing the remediation of a site in SE London for housing. It'd had a few subsequent uses (road haulage depot was one I recall) but the primary pollution problem was it having been previously used as a town-gas site.
The Developer had bought the site for nun-pence from the local authority, but we then spent several million £s, digging out and carrying away (to Cambridgeshire and even Derbyshire for the really nasty stuff) several thousand tonnes of the worst of the crap (lots of aresenic), backfilling those excavations with hardcore, then four layers of sealed heavy plastic and a 150mm layer of fresh concrete, through which we drove and subsequently sealed around all the foundation piles. Covered that slab with a 0.80-1.50m layer of more clean hardcore, then terram fabric and final toppings; all the house-slabs too were sealed and vented. I understood that at that time it was 'the most polluted site in Western Europe to be used for residential development'.
Even after all that clean-up/capping/sealing work, the property sales contracts still carried a clause precluding the growing of any fruit or vegetables in the gardens; then again, it was London, so the gardens were barely big enough for a bunch of carrots anyway.

 

[Lon nan Gruagach]

Then theres red lead oxide putty...
A 150 year old cast iron rim and steel bucket water wheel came apart using spanners thanks to Whitworth threads and red lead oxide putty.

 

[Ship'sCat]

Then theres red lead oxide putty...
A 150 year old cast iron rim and steel bucket water wheel came apart using spanners thanks to Whitworth threads and red lead oxide putty.

Its funny you should mention this because the threads of the bolts from my cast iron keel which started all of these posts seems to have red lead oxide putty………..as well as of course tar, it seems, on their shanks.

 

[AntarcticPilot]

Wrong, I'm afraid. Many decades ago my mother worked in occupational health for a Gas Board, and one of her jobs was to look out for "pitch warts". A pitch wart or hydrocarbon keratosis is a type of skin reaction to several chemicals that cause epidermal hyperplasia, which may be associated with tumor or cancer formation. Certain petroleum intermediates and products, retorted shale oil, coal liquification intermediates, a number of coal tar derivatives and arsenic can stimulate the epidermal cells to produce these effects. See, for example, http://www.hse.gov.uk/pubns/indg435.pdf

Thanks! I think I've escaped the consequences; it is nearly 50 years since I worked for CTRA, and no problems yet - the odds must have come down on my side!

 

[AntarcticPilot]

That makes more sense. I was surprised by OK's comment having many years ago been involved with managing the remediation of a site in SE London for housing. It'd had a few subsequent uses (road haulage depot was one I recall) but the primary pollution problem was it having been previously used as a town-gas site.
The Developer had bought the site for nun-pence from the local authority, but we then spent several million £s, digging out and carrying away (to Cambridgeshire and even Derbyshire for the really nasty stuff) several thousand tonnes of the worst of the crap (lots of aresenic), backfilling those excavations with hardcore, then four layers of sealed heavy plastic and a 150mm layer of fresh concrete, through which we drove and subsequently sealed around all the foundation piles. Covered that slab with a 0.80-1.50m layer of more clean hardcore, then terram fabric and final toppings; all the house-slabs too were sealed and vented. I understood that at that time it was 'the most polluted site in Western Europe to be used for residential development'.
Even after all that clean-up/capping/sealing work, the property sales contracts still carried a clause precluding the growing of any fruit or vegetables in the gardens; then again, it was London, so the gardens were barely big enough for a bunch of carrots anyway.

I should have remembered that - my Mum's house was built on the site of an old gas works, and (after a legal battle about responsibility) the local council ended up having to carry out remediation including (as you describe) removal of earth down to some level. The pollutants were both inorganic(Arsenic) and organic. There was a question for a while whether one house (not my mother's) would have to be demolished to allow full remediation. Of course, that severely affected the value of the house when I (as my mother's executor) came to sell it.

 

[vyv_cox]

Thanks! I think I've escaped the consequences; it is nearly 50 years since I worked for CTRA, and no problems yet - the odds must have come down on my side!

Unlike my time bomb - asbestos. When I worked with it more than 50 years ago we were in a perpetual cloud of the stuff. A colleague died many years ago from asbestosis, that apparently can lurk for many years before suddenly making itself known. Fingers crossed for many years now.

 

[wombat88]

mix sand into the tar and paint the bottom of your clinker dinghy with it. It won't leak for a while...

 

[fisherman]

mix sand into the tar and paint the bottom of your clinker dinghy with it. It won't leak for a while...

the local crabbers, about 25ft, sawn frames, and after many years of bouncing over elm timbers to launch, leaking like sieves, would be treated with tar and sawdust, and/or a flaming torch run around the bottom. None of them could survive a night on a mooring. They didn't rot though.

 

[Ohlin Karcher]

Wrong, I'm afraid. Many decades ago my mother worked in occupational health for a Gas Board, and one of her jobs was to look out for "pitch warts". A pitch wart or hydrocarbon keratosis is a type of skin reaction to several chemicals that cause epidermal hyperplasia, which may be associated with tumor or cancer formation. Certain petroleum intermediates and products, retorted shale oil, coal liquification intermediates, a number of coal tar derivatives and arsenic can stimulate the epidermal cells to produce these effects. See, for example, http://www.hse.gov.uk/pubns/indg435.pdf

Very interesting, thanks for the link.
I can see why these things are restricted use or banned, because, as the link says, people who work with them in skin contact for months or years may get warts, which might be cancerous. That suggests that they are safe for occasional use though, doesn't it?

 

[rogerthebodger]

I bought a couple of litres of two pack epoxy tar in NZ last year.

Kiwi farmers use it for waterproofing sheep and cattle drinking water tanks on their farms, as well as waterproofing roofs.

I used it in the gas locker of our steel Hartley 32 which was very rusty due to splashback from the exhaust getting in the overboard drain holes when motoring.

Rubber flap covers over the drain ports has halted the water ingress and I am told by the friend who looks after the boat that the gas locker is rust free now.

It remains slightly flexible when cured and might well be the answer if proper tar cannot be found.

Credit where credit is due, the Steel Boat evangelist Brent Swain or one of his acolytes reccomended its use, so, thank you.

I also use coal tax epoxy on both my steel boat and ferro boat below the waterline.

Easy to obtain local to me here

http://abe.co.za/wp-content/uploads...micals-general-construction-ds_abecote352.pdf

 

[vyv_cox]

Very interesting, thanks for the link.
I can see why these things are restricted use or banned, because, as the link says, people who work with them in skin contact for months or years may get warts, which might be cancerous. That suggests that they are safe for occasional use though, doesn't it?

I don't have much knowledge of the health aspects of coal tar but I have researched methylene chloride paint stripper on several occasions. This is the stuff that Nitromors used to contain but following deaths of regular industrial users it was given a world-wide ban. Despite that it is widely available: I have bought it under the name Starchem Synstrip. It is very unpleasant stuff indeed, see the MSDS at http://www.megaloid.ca/MSDS/Methylene Chloride.pdf It is use in industry, particularly auto refinishing where largely untrained people slap it on without proper precautions, that is particularly concerning. I would only use it outdoors with very adequate PPE.

 

[claudia_borresen_67]

Way back in the dim and distant past, we used to heat bolts etc to a "good black" heat (ie not even slightly red hot), and then plunge them into liquid tar. This burned the tar onto the bolts, or other metal fittings, giving them an impermeable skin to prevent corrosion. Possibly that is what has been done with your keel bolts. The "tar" was readily available at any town gas works. I remember going with a 5 gallon drum, and I think they practically gave it away. I'm sure there are better methods nowadays.

Hi NormanS - I am trying to implement this method myself. However, I am having little success in getting it to work. I tried it by heating a mild-steel rod with a torch just until it becomes dark and dipped it in a tube half filled with Stockholm pine tar. As I only half dipped the rod, I was expecting to spot the differences - unfortunately, could not see any difference between the dipped and un-dipped zone.
Do I need to repeat the cycle multiple times until it starts building up a visible layer? Any idea what temperature should the material be?
Thanks

 

[NormanS]

Hi NormanS - I am trying to implement this method myself. However, I am having little success in getting it to work. I tried it by heating a mild-steel rod with a torch just until it becomes dark and dipped it in a tube half filled with Stockholm pine tar. As I only half dipped the rod, I was expecting to spot the differences - unfortunately, could not see any difference between the dipped and un-dipped zone.
Do I need to repeat the cycle multiple times until it starts building up a visible layer? Any idea what temperature should the material be?
Thanks

That's a bit of a blast from the past!
The system of "Hot Dipping" used coal tar, which was a byproduct in the production of Town Gas. At one time, many even quite modest little towns would have a Gas Works, particularly in parts of the country where suitable coal was available. Another byproduct was coke, an early form of smokeless fuel. That's all gone now, and I imagine that Coal Tar is unobtainable.
Probably, a modern equivalent would be the hot poured pitch, used extensively for sealing around minor road repairs.
I don't know what temperature the steel should be taken to, but just short of red hot would be about right. It's definitely a one dip process, not a gradual build-up.
Personally, I would go for a more modern process, like galvanising.

 

[AntarcticPilot]

That's a bit of a blast from the past!
The system of "Hot Dipping" used coal tar, which was a byproduct in the production of Town Gas. At one time, many even quite modest little towns would have a Gas Works, particularly in parts of the country where suitable coal was available. Another byproduct was coke, an early form of smokeless fuel. That's all gone now, and I imagine that Coal Tar is unobtainable.
Probably, a modern equivalent would be the hot poured pitch, used extensively for sealing around minor road repairs.
I don't know what temperature the steel should be taken to, but just short of red hot would be about right. It's definitely a one dip process, not a gradual build-up.
Personally, I would go for a more modern process, like galvanising.

It's likely that modern materials are derived from bitumen rather than coal tar. Bitumen has similar physical properties to coal tar, but is chemically different; coal tar has aromatic compounds (i.e. benzene rings), while bitumen is aliphatic (i.e. carbon chains). Pitch can be derived from either, but is basically stuff left behind after all the lighter fractions have been distilled off, and pitch from coal tar differs chemically from pitch from bitumen in the same way.

Stockholm tar is different again, being derived from the destructive distillation of wood. But I know less about it's chemistry and properties than I do coal tar and bitumen. I'd suspect that terpenes are prominent in its composition, but that's a guess.

 

[claudia_borresen_67]

Personally, I would go for a more modern process, like galvanising.

That's the conclusion I have been funneled to after posing the same question in different forums as well. The multiple sources I read werent ever clear if it should be pitch tar (or similar) or pine tar (like the one I have). As much as I would like to use a traditional method and the pine tar I already have, I realize now that I have the wrong tar and I should perhaps go and find a galvanizer around here (SW of the UK) to do the bolts, instead.