What is "Tar" for a boat owner?

[Ship'sCat]

At present I am going through the process of taking out sample keel bolts from my 1968 GRP yacht which has a cast iron keel. The keel is fixed to the hull with flanges each side of its top edge, so the ends of the bolts are visible from outside. They are easy to knock out once the nuts are removed internally.
So far I am impressed at the good condition of the sample bolts taken out so far, especially as they have been there years and years, according to the previous owner. I notice that the shanks of the bolts are black as if they were dipped in tar. I remember an old ship repairer in Fraserburgh once telling me that there is nothing like tar for proofing steel against rust. This inclines me to dip the bolts in tar prior to putting them in, whether new replacement or existing.
But how do I find "tar"? For this purpose does it mean "bitumen"? Do I go up to a gang of Boys from the Black Stuff and ask them for a lump of the black stuff they out put in their pot to melt into gravel? Or is "tar" for boat purposes different stuff? And is "pitch" the same or different again? And where can I get the right stuff?

 

[vyv_cox]

Tar and bitumen are not the same.

Tar contains many organic products including aromatics and as such have been banned as being carcinogenic.

Bitumen is a high molecular weight hydrocarbon that remains after almost everything else has been distilled from crude oil. It would be difficult to use for corrosion protection in this application.

Pitch is similar to tar and is also likely to be unobtainable.

Unfortunately you are limited to current commercial products that may offer reduced corrosion protection but are safe for users and manufacturers.

 

[NormanS]

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.

 

[JumbleDuck]

Tar contains many organic products including aromatics and as such have been banned as being carcinogenic.

 

[Lon nan Gruagach]

You could make some tar.
Fill a pressure cooker with nice juicy pine, close the lid and stick it in a (small) fire...

No, it wont explode since all the oxygen will be expelled before it gets hot enough.

 

[jant]

https://captainwatts.co.uk/stockholm-tar

 

[Norman_E]

Stockholm Tar is tar made from wood, either pine or beech being the main woods used. It is more liquid than the coal tar that used to be available, but there is no reason why it won't do the job of excluding moisture if applied to steel bolts. It is sold for many uses including protecting horses hooves. If buying it I suggest asking how liquid it is and whether it is pure or contains other substances, as you want it as thick and viscous as possible. Telegraph poles used to be protected from rot by Stockholm Tar impregnation and the stuff used on them was very thick at room temperature.

 

[Ohlin Karcher]

Proper traditional coal tar is definitely still available, it is used for paying seams on historic ships, etc.
Google caulking irons, seam tar etc, there are a couple of online British suppliers.
It is totally harmless for your purposes, don't worry about alarmist cancer scares and petty bureaucrats' regulations.
The same applies to real creosote.
Although I would also look at Sikaflex and high-tech constuction mastics, there are some amazing products out there.

 

[vyv_cox]

Years ago I painted the keel of my first boat with coal tar epoxy, I believe it was an International product. Later I found it had been withdrawn and replaced with a far inferior product with the same name. Several suppliers of coal tar epoxy can be found by Google but the ones I have looked at have also withdrawn the product, e.g. https://www.epoxyproducts.com/coaltar.html Rustoleum say they still make it but not sure if that is current.

 

[pcatterall]

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.

I seem to recall that many early iron structures were protected in this way ( though I thought it was via burning oil on the metal) Engineers carrying out repairs were surprised that the exposed iron had lasted so well.

 

[rotrax]

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.

 

[macd]

Tar and bitumen are not the same.

I've no doubt that's right, Vyv, but there's lots of ambiguity in usage. Bitumen (aka asphalt, pitch) is the stuff that makes natural tar lakes.

There are certainly few things better than coal tar for sealing wood, especially end-grain. (I used the stuff years ago, but production more or less ended when local gas works disappeared.) As Norman wrote, pine tar, aka Stockholm tar, seems still to be available, but whether in the highly viscous form required here, I've no idea. Perhaps a query on the Classic Boat forum might be worthwhile?

 

[Pasarell]

Coal tar, as used in coal tar epoxy was banned as carcinogenic many years ago, probably early 90's. Most coatings manufacturers replaced with a synthetic tar for some years which was just as good. Nowadays not many make it as technology has moved forwards but probably some of the smaller companies still have synthetic tar products. Might be worth contacting Teamac or Leighs

 

[vyv_cox]

I've no doubt that's right, Vyv, but there's lots of ambiguity in usage. Bitumen (aka asphalt, pitch) is the stuff that makes natural tar lakes.

As you say Mac, lots of ambiguity (ignorance ) Natural tar contains a wide variety of compounds but bitumen comprises only long chain hydrocarbons and is a very specific product of distillation. Tar that was produced by coke ovens was very different from bitumen.

 

[AntarcticPilot]

As you say Mac, lots of ambiguity (ignorance ) Natural tar contains a wide variety of compounds but bitumen comprises only long chain hydrocarbons and is a very specific product of distillation. Tar that was produced by coke ovens was very different from bitumen.

+1 for Vyv's explanation; tar and bitumen are not the same. My first ever job was at the Coal Tar Research Association's laboratories in Gomersall (long defunct!), and much of the work we were doing was to look at replacing coal tar with bitumen. Coal tar comes in two types that also have different properties - high temperature tar, which results from the production of old fashioned town gas, and low temperature tar that results from the production of smokeless fuels, and which is likely to be the only kind readily available these days. Bitumen, high temperature tar and low temperature tar all have different properties and chemical compositions, though the two coal tars are closer to each other than to bitumen. Pitch is the residue after distilling tar to obtain the volatile products.

And, I'm afraid 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!). Basically, most of the traditional uses of coal tar rely on it being poisonous, so that shouldn't be a surprise. Bitumen is a lot safer, being made of aliphatic carbon compounds that are less reactive.

 

[NormanS]

When I had a boat with a proper laid deck, caulked with oakum, the seams were sealed by pouring pitch into them with a ladle. The pitch came in solid form, jet black and shiny, and had to be broken up, then heated in a pot until very runny before carefully pouring it. I never used tar for this.

 

[AntarcticPilot]

When I had a boat with a proper laid deck, caulked with oakum, the seams were sealed by pouring pitch into them with a ladle. The pitch came in solid form, jet black and shiny, and had to be broken up, then heated in a pot until very runny before carefully pouring it. I never used tar for this.

Pitch results from the distilation of tar to remove volatile fractions. It's basically the high molecular weight fraction of tar. It's properties vary with the source and with the amount of volatiles removed.

 

[JumbleDuck]

Years ago I painted the keel of my first boat with coal tar epoxy, I believe it was an International product. Later I found it had been withdrawn and replaced with a far inferior product with the same name. Several suppliers of coal tar epoxy can be found by Google but the ones I have looked at have also withdrawn the product, e.g. https://www.epoxyproducts.com/coaltar.html Rustoleum say they still make it but not sure if that is current.

I suspect that the disappearance of coal tar is mainly due to the disappearance of coal. It used to be a cheap byproduct - practically a waste product - of gas production, and at Biggar gas works you can see where the coal tar was collected for sale. Curiously enough, coal (town) gas was discovered as a by product of heating coal to produce tar.

 

[JumbleDuck]

Coal tar, as used in coal tar epoxy was banned as carcinogenic many years ago, probably early 90's.

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?

 

[fisherman]

I think there may be a world of difference between 'black iron' bolts as used 50, 60 or more years ago and the range of qualities available now. One wooden F/V, 1980 vintage, had to have keel bolts replaced after about 15 years, and that was from a very reputable builder. Not to say there hadn't been some other neglect, eg anodes, and I've seen fairly spectacular results, allegedly from loose live wires left in the bilge.