Hot dipped keel bolts in pine tar

[Claudia_Borresen_67]

Hello forum, I have read in multiple places about a protective coating method for steel bolts (not exclusively for bolts) consisting in dipping pre-heated bolts (to a "black heat") in pine tar. However, I could not find a detailed description of this method nor what to look for to determine a pass or a fail.
I tried to do it myself by heating a mild-steel rod with a torch 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.

Would any one be able to point me in the right direction or provide me some guidance here? Is this even an effective protective method?

Thank you!

[wizbang 13]

Sorta like with galvanizing, the atoms move aside when hot to let the zinc in between the steel atoms?
never really heard of it.
Are you looking for a good way of sending keel bolts home or rust prevention in general?
Bruce

[sp_clark]

Never done that but have to ask: wouldn't pre-heating bolts tend to 'cook off' whatever organic sticky'd they'd be dipped into? Seems counter-intuitive IMHO.

You want to coat something metallic, get away with a decent coating you want the sticky stuff warm enough to flow then cling as the cooler bit's dunked, then slowly removed, no?

[wizbang 13]

I coated my galv . Keel bolts with straight epoxy, then later slathered them with regular roof goo, stuff for rolled roofing.
I pulled one when the boat was 25 yo,was perfect. I should pull another for her 40th.

[wizbang 13]

I’m wondering how close you came to detonating that can of pine tar?

[Claudia_Borresen_67]

I have a cast iron ballast keel with steel bolts going through an oak timber keel. My intension is primarily to create a protective (impermeable) layer between the bolts and the oak. Additionally, general rust prevention of the bolt head and nut is an added bonus, although that can be achieved by other means.

[wizbang 13]

Can you achieve this by locking up the end grain of the oak ? Over drilling the oak, fill with solid epoxy, then re bore the hole thing.
Are they out or coming out ?

[Claudia_Borresen_67]

I am also considering protecting the end grain in a similar way.
Although, if I can, I would prefer to add an extra protection.

[Peerie Maa]

Can you achieve this by locking up the end grain of the oak ? Over drilling the oak, fill with solid epoxy, then re bore the hole thing.
Are they out or coming out ?

No. Bolts in boats should be driven tight to prevent the working of the hull fretting the bolt holes and causing nail sickness. Keel bolts should be driven in a 1/16th" undersize hole.
A better way would be to dip the bolts hot into pitch or roofing tar just before driving them. That coats the zinc ans seals the grain of the wood. Similar to your post #4.

[heimlaga]

In the past before hot dip galvanizing became affordable dipping heated bolts and nails in pine tar and later coal tar was common practice. Pretty much every boatbuilder and every ship yard along the coast of Finland did it. My grandfather saw it being done in the 1920-ies or 30-ies but then it wasn't common anymore. Getting the heat exactly right is critical. If no tar is left on the iron you had it way too hot.

[Peerie Maa]

Hello forum, I have read in multiple places about a protective coating method for steel bolts (not exclusively for bolts) consisting in dipping pre-heated bolts (to a "black heat") in pine tar. However, I could not find a detailed description of this method nor what to look for to determine a pass or a fail.
I tried to do it myself by heating a mild-steel rod with a torch 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.

Would any one be able to point me in the right direction or provide me some guidance here? Is this even an effective protective method?

Thank you!

That is called Scotch galvanizing. Used on wrought iron (which rusts far less than other iron alloys like steel) when hot dip galvanizing was unavailable.

[sp_clark]

Getting the heat exactly right is critical. If no tar is left on the iron you had it way too hot.

What prompted my earlier post.

No. Bolts in boats should be driven tight to prevent the working of the hull fretting the bolt holes and causing nail sickness. Keel bolts should be driven in a 1/16th" undersize hole.
A better way would be to dip the bolts hot into pitch or roofing tar just before driving them. That coats the zinc ans seals the grain of the wood.

I can understand the thinking on this but with undersized hole taking heated, coated steel bolts being driven in, would pre-coating the hole with heated tar help at all?

Both as a lubricant as well as to prevent the bolt going in from losing most of its coating as it proceeds from hole top to bottom? Friction alone would tend to keep coating liquid whilst smaller hole'd tend to scrape it off?

[Claudia_Borresen_67]

As much as I would like to use a traditional method and the pine tar that I already have, I should perhaps go and find a galvanizer to do the bolts, instead.

[Peerie Maa]

I can understand the thinking on this but with undersized hole taking heated, coated steel bolts being driven in, would pre-coating the hole with heated tar help at all?

Both as a lubricant as well as to prevent the bolt going in from losing most of its coating as it proceeds from hole top to bottom? Friction alone would tend to keep coating liquid whilst smaller hole'd tend to scrape it off?

Pre-coating the hole would also be a good idea. The bolts still must be driven tight, which precludes a fragile coating.

[ahp]

A docent told me (I think) many years ago at Mystic Seaport that they coated wroght iron hardware by dipping the piece into a mixture of hot turpintine and pine tar.

[Claudia_Borresen_67]

What about powder coating? Any reason to avoid it?

[sp_clark]

As much as I would like to use a traditional method and the pine tar that I already have, I should perhaps go and find a galvanizer to do the bolts, instead.

Both!

Tar's used to seal end grain in wood probably more than reduce corrosion of steel fasteners.

You can't source suitable galvanized steel bolts where you are? Ought to be cheaper than finding a hot-dip galvanizing source anywhere near local to you. Threads will increase in size too if you have plain steel dipped; I believe bolts intended for galvanizing have threads cut to compensate for the build-up of zinc. Same done w/nuts to go with bolts.

Powder-coating may work to protect steel but the wood needs the tar even more.

[P.I. Stazzer-Newt]

Powder coating is relatively fragile.

[Claudia_Borresen_67]

You can't source suitable galvanized steel bolts where you are? Ought to be cheaper than finding a hot-dip galvanizing source anywhere near local to you.

The bolts are all of different sizes. I actually had to make them myself on a lathe from a 20mm mild steel rod. I doubt I could find anything off-the-shelf.

Powder-coating may work to protect steel but the wood needs the tar even more.

Yes, powder coating only for the bolts. The oak still needs to be sealed as well.

[wizbang 13]

No. Bolts in boats should be driven tight to prevent the working of the hull fretting the bolt holes and causing nail sickness. Keel bolts should be driven in a 1/16th" undersize hole.
A better way would be to dip the bolts hot into pitch or roofing tar just before driving them. That coats the zinc ans seals the grain of the wood. Similar to your post #4.

This sounds like a one way trip for the keelbolts Nick.
We don’t know how thick or deep or old is the oak yet.
Wouldn’t there be a danger of the bolts seizing in there or splitting the keel from rust?
B

[Peerie Maa]

This sounds like a one way trip for the keelbolts Nick.
We don’t know how thick or deep or old is the oak yet.
Wouldn’t there be a danger of the bolts seizing in there or splitting the keel from rust?
B

Sizing in there is not a problem, you do not want the bolts moving at all in any direction. If the bolt is rusted enough to split the wood, it needs to be replaced anyway.

[Edward Pearson]

'Blackening steel' is an old school rust prevention.

Video of Steve Jordan blackening a lathe part with engine oil.

I think you just needed two repeat it several times until it goes black(er).

[sp_clark]

'Blackening steel' is an old school rust prevention.

"Parkerizing" too, done with phosphoric acid and magnanese dioxide.

If you can make your own steel bolts on a lathe you can do backyard Parkerizing as well.

It's just not that hard but there are some hazards involved with preparing and using hot liquids and acid so be prepared to be careful.

There's also a process that uses zinc instead of manganese, may be more appropriate for protection from saltwater.

Admitting I've not heard much about this used for treating parts used on boats, I'm tossing it out here to give others an opportunity to add their comments as to whether it has any utility for Claudia's project.

[John Meachen]

Black oxide is a quick and cheap system for steel,but does very little to delay the onset of corrosion.It is often encountered on machine parts and likes to be lightly coated with oil.I seem to remember the late John Teale describing the process of using heat and tar in one of his books.If real galvanising is an option,it would probably be the best thing.Driving any bolt through an undersize hole pretty much guarantees it will be a nightmare to remove and ferrous metals corroding in oak will really get a grip.As an aside,I knew an older boatbuilder who would now be nudging 90 or so and who once helped with building a wooden trawler that the regulators insisted had to have bolts driven through 1/8" undersize holes and from the second hole onwards they used exact sized holes and still fought the bolts.I have had a go at removing exactly one and it would have destroyed the keel and probably the bolt if I had persisted.I have no idea what would be the ideal long term solution as it will need to be taken apart sooner or later,even if the deterioration is only detected by X-ray or other sophisticated techniques.

[Peerie Maa]

Black oxide is a quick and cheap system for steel,but does very little to delay the onset of corrosion.It is often encountered on machine parts and likes to be lightly coated with oil.I seem to remember the late John Teale describing the process of using heat and tar in one of his books.If real galvanising is an option,it would probably be the best thing.Driving any bolt through an undersize hole pretty much guarantees it will be a nightmare to remove and ferrous metals corroding in oak will really get a grip.As an aside,I knew an older boatbuilder who would now be nudging 90 or so and who once helped with building a wooden trawler that the regulators insisted had to have bolts driven through 1/8" undersize holes and from the second hole onwards they used exact sized holes and still fought the bolts.I have had a go at removing exactly one and it would have destroyed the keel and probably the bolt if I had persisted.I have no idea what would be the ideal long term solution as it will need to be taken apart sooner or later,even if the deterioration is only detected by X-ray or other sophisticated techniques.

Ted Frost, writing about building wooden steam herring drifters in 1916 at Lowestoft, talked about boring the boltholes 1/16th undersize. These were the galvanized bolts used to secure the oak planking to the frames.

[debenriver]

We used to heat iron (not steel) bolts to near red heat and then dip them in tar – so the tar sizzled on the bolts. But they were then left to cool before being driven. I don't recall ever having undersize holes through the wood keel as that would make driving the bolts home pretty difficult.

The ballast keel was generally bolted to the assembled centreline structure (wood keel – stem and apron – sternpost and knee) laid on its side, so the ballast keel could be slid up to it and the bolts driven horizontally. Then the whole assembly could be righted for the moulds to be assembled on it, for ribbands, timbering, planking etc.

I differ from Nick here that undersize holes through the wood keel are necessary – as long as the bolts are heaved up tight with good big square washers under the nuts (and usually forged tapered heads in the ballast keel), there is no likelihood of any movement. At that time keel bolts generally only passed through the wood keel - not the floors: they had separate bolts up through the wood keel only.

Mind you it was also common at that time to bed the ballast keel on a mixture of horse dung and straw ... I can well remember being sent up to my grandfather's stable for the horse dung!

True wrought iron or crown iron corrodes less easily than mild steel of course, so probably hot dipping in tar was sufficient. With mild steel, hot dip galvanizing must be a much better option.

Cheers -- George

[Dave Hadfield]

There are 80 year old galvanized fasteners in Drake that are not rusting -- for which I'm profoundly grateful. Hull and decks.

True, it's a Great Lakes boats, not salt-water. But as a certain Canadian once said, "Rust never sleeps".

Although I use pine-tar at the very slightest motivation -- love the stuff -- there is no indication that the bolts or holes were ever exposed to it.

IMG_1505.jpg

[Claudia_Borresen_67]

Ted Frost, writing about building wooden steam herring drifters in 1916 at Lowestoft, talked about boring the boltholes 1/16th undersize. These were the galvanized bolts used to secure the oak planking to the frames.

Bud McIntosh suggests the same undersized boltholes in his book. Not sure about the exact dimensions but I remember they differ depending on the hardness of the wood.

We used to heat iron (not steel) bolts to near red heat and then dip them in tar – so the tar sizzled on the bolts. But they were then left to cool before being driven.

Was that coal tar? And would it harden as it cools? Today I did a similar experiment with stockholm pine tar. As it cooled down, the tar remained gooey - the moment I would drive them through a tight bolthole, all the tar would be scraped of - it cant be right, right?

True wrought iron or crown iron corrodes less easily than mild steel of course, so probably hot dipping in tar was sufficient. With mild steel, hot dip galvanizing must be a much better option.

I have considered this option. it was just too expensive especially if you consider that I could not find anyone in the UK that would forge them to the right dimension. The only foundry I found only worked with imperial moulds. I need 20mm and next size up would mean too much turning to bring it down to 20mm.

[jpatrick]

The notion of drilling undersized holes before driving the bolts must certainly depend on the species and moisture content of the timber being drilled. Green wood will more easily yield to the oversized fastener whereas dry will resist.

As to the idea of "parkerizing" or similar treatment of mild steel is just fine for gun barrels, shop tools, and the like. But for keel bolts, not so much. Try it on a sample of mild steel, then put the sample into salt water. See how long it lasts.

Jeff

[wizbang 13]

Galvanize them. Coat three times with interlux 2000 . Slather with roof goo . Install in a hole bored in 404 thickened epoxy with some room for the roof goo.
We are in a new century here .
Keel bolts are not rusty drifts made to rely on rust to hold them tight and be thrown away after a decade or two.

[Bruce Brown]

I'm with Bruce on this one. After puzzling on this same problem, I settled on galvanized bolts, pour epoxy into a same diameter hole, dip the bolt in epoxy, drive, Bob's yer uncle. No long-term follow-up, but I'll be gone by then.

[wizbang 13]

I'm with Bruce on this one. After puzzling on this same problem, I settled on galvanized bolts, pour epoxy into a same diameter hole, dip the bolt in epoxy, drive, Bob's yer uncle. No long-term follow-up, but I'll be gone by then.

im not saying to glue in the keel bolt.

[Boatbum]

I had a boat builder that drilled the bolt hole a little bigger to facilitate the insertion of a fiberglass sleeve and then the blot was inserted through that - it separated the steel form the keel plank very nicely.

[peter radclyffe]

Wessex Galvanizers Ltd - Wedge (wedge-galv.co.uk)

[sp_clark]

I think it may help clarify things if we knew what the keel's dimensions are (depth mostly but width'd help) and the length of the bolts you've made that have to pass thru that keel.

In any case they shouldn't be 'glued' into the keel, but reinforcing the keel against compression forces by 'pillar-bedding' by some means will lengthen keel life. As will sealing the end grain exposed by drilling of thru-holes, whether with tar or epoxy, or even suitable paint perhaps.