"Old Steel" and the tale of two surveys

[Slow and Steady]

When you are dealing with 0.8mm thick car bodywork on old classics that rust from the inside where they weren't painted, rust properties do matter. When you find modern sheet of this thickness is floppy like lead and older stuff is stiff and shrinks less when you weld it that matters too and my experience is that these two things are true. So, maybe it's technically possible for modern steel to be better but simply stating that it is better is demonstrably not true for all steel. I don't care what the spec sheet says, I spent 8 years full time making things out of steel sheet and my experience is as I describe.

 

Perhaps there is something in the process of rolling steel that has changed. I do know that steel from a burnt out car is much softer.

[MtB]

7 minutes ago, Slow and Steady said:

I do know that steel from a burnt out car is much softer.

 

I'd suggest this is understandable, to be expected even. The pressing of steel into shape will introduce some work-hardening which makes the steel more rigid and hard. During a fire, the heat will aneal the steel returning it to a softer, floppier condition.

[Captain Pegg]

5 minutes ago, Slow and Steady said:

When you are dealing with 0.8mm thick car bodywork on old classics that rust from the inside where they weren't painted, rust properties do matter. When you find modern sheet of this thickness is floppy like lead and older stuff is stiff and shrinks less when you weld it that matters too and my experience is that these two things are true. So, maybe it's technically possible for modern steel to be better but simply stating that it is better is demonstrably not true for all steel. I don't care what the spec sheet says, I spent 8 years full time making things out of steel sheet and my experience is as I describe.

 

Perhaps there is something in the process of rolling steel that has changed. I do know that steel from a burnt out car is much softer.

 

But that's not what we're dealing with and those panels rust from the inside because they weren't painted as you say. That is also what happens to boat baseplates. They rust from the inside rather than the outside but it's nothing to do with the steel, it's about the environment and the applied protection.

 

If it behaves markedly differently in a mechanical way then it's not the same product. One thing I think is probably true of steel narrowboats built for leisure use is that 99% are built with S275 (that's Grade 43 for the old timers) mild steel.

[Slow and Steady]

3 minutes ago, Captain Pegg said:

 

But that's not what we're dealing with and those panels rust from the inside because they weren't painted as you say. That is also what happens to boat baseplates. They rust from the inside rather than the outside but it's nothing to do with the steel, it's about the environment and the applied protection.

 

If it behaves markedly differently in a mechanical way then it's not the same product. One thing I think is probably true of steel narrowboats built for leisure use is that 99% are built with S275 (that's Grade 43 for the old timers) mild steel.

Indeed - if you look back I did point out that in the case of boats all this doesn't really matter - my point (and I'm sticking to it) is that in general commonly stocked sheet steel ain't what it used to be. This does make sense - "stuff" used to be made to last and manufacturers made their reputations on that. Now stuff is expected to be chucked in short order and the cheaper it can be made the better. There is simply no point in using high grade materials where the physical properties don't matter, but in "the old days" better materials were used even if the only reason was pride.

[Captain Pegg]

1 minute ago, Slow and Steady said:

Indeed - if you look back I did point out that in the case of boats all this doesn't really matter - my point (and I'm sticking to it) is that in general commonly stocked sheet steel ain't what it used to be. This does make sense - "stuff" used to be made to last and manufacturers made their reputations on that. Now stuff is expected to be chucked in short order and the cheaper it can be made the better. There is simply no point in using high grade materials where the physical properties don't matter, but in "the old days" better materials were used even if the only reason was pride.

 

Have you never considered that the world of engineering and technology moves forward rather than backward and why it is that buildings get taller and bridge spans get longer, or why the standard National Grid lattice tower design from the 1920s has finally been replaced with a single pole?

 

It's because the material science has moved on.

[Slow and Steady]

14 minutes ago, Captain Pegg said:

 

Have you never considered that the world of engineering and technology moves forward rather than backward and why it is that buildings get taller and bridge spans get longer, or why the standard National Grid lattice tower design from the 1920s has finally been replaced with a single pole?

 

It's because the material science has moved on.

It's capabilities have moved on. Have you ever considered why consumer stuff falls to pieces in short order these days? Consumerism has moved on. I mean, I bought a convector heater a few years ago that went up in smoke within a few days. High current wiring was connected with spade connectors and thin wire used. Whatever the possibilities it doesn't follow that best practice is followed and I would argue that the further material science progresses, the closer to the bone everything is cut. You pick examples that simply do not apply to anything I will buy/own. Stuff I buy has been downgraded over the years to the extent that it seems acceptable to sell things that merely look like what they are supposed to be and are completely unfit for purpose.

[Captain Pegg]

7 minutes ago, Slow and Steady said:

It's capabilities have moved on. Have you ever considered why consumer stuff falls to pieces in short order these days? Consumerism has moved on. I mean, I bought a convector heater a few years ago that went up in smoke within a few days. High current wiring was connected with spade connectors and thin wire used. Whatever the possibilities it doesn't follow that best practice is followed and I would argue that the further material science progresses, the closer to the bone everything is cut. You pick examples that simply do not apply to anything I will buy/own. Stuff I buy has been downgraded over the years to the extent that it seems acceptable to sell things that merely look like what they are supposed to be and are completely unfit for purpose.

I don’t dispute that but it’s going off track of the original premise which was that older steel is better quality than modern steel.

 

It’s equally possible to cheaply and poorly manufacture something from either but the point was about the primary material.

 

Modern steel making processes continue to improve the product, as they have since the first commercially viable steels were produced. But it hasn’t and never will stop carbon steel from rusting.

[john.k]

I asked a guy I know about the single pole towers....he says they are terrorist proof compared to the bolted lattice towers.

[DShK]

10 hours ago, Slow and Steady said:

ref cars and old steel I have experience here and sorry but it's true certainly regarding old Volkswagons from the 60's compared to the 70's. The older stuff is like rock and does not warp (shrink/expand) to anywhere near the extant the more modern stuff does. There are quite a few restorers who specialise in old VW vans and some of them will only work on the older ones for this reason. Roll on a few more decades and pattern part body panels - so weak and bendy you wonder if they are made from lead sheet! This probably doesn't apply to stock sheet steel boats are made from, but the quality of steel CHOSEN by some car makers is by no means a constant thing.

 

I used to make some panels from old stock steel shelving after acquiring a heap of it and it was like magic. Without a doubt it corroded much more slowly than more modern steel sheet and this was just shelving, nothing special. There are sooo many different types of steel and steel used to be cheap enough that better quality recipes were used.

 

Check this out - the shiny bright bit and the rusty bit were both cleaned up at the same time and left a couple of days.

The shiny is ex 1940s/50s shelving below the weld, 1968 above, the rusty is 2010 sheet steel.

Funny because I grew up with parents who were classic VW enthusiasts and they rotted like nobody's business! In fact their first VW camper (1960s t2 bay window) was scrapped because the entire chassis was made of rust.

[DShK]

9 hours ago, Captain Pegg said:

No one in the world of engineering or metallurgy considers the quality of steel in terms of whether it is prone to rusting or not.

 

What they know is that carbon steel - which accounts for 80% of production and almost 100% of steel narrowboats - is basically 99% iron and has a chemically unstable surface. This is why mill scale forms on the surface during production and rust forms when exposed to normal atmospheric conditions. All carbon steel will rust and while surface condition does have an affect, as does the exact chemical composition (early Bessemer steels have some chemical similarity to wrought iron and do rust less readily than later steels), in terms of the mechanical properties it isn't important. They also know of a substance called paint. Nonetheless I know of applications of uncoated carbon steel in outdoor use. This is possible because normal rusting doesn't happen at a significant rate.

 

If corrosion protection is paramount and coating isn't possible then high alloy steel i.e. stainless is specified.

 

I generally consider anyone who uses the term quality in this context doesn't really know what they are talking about. In specifying steel the term quality generally refers to the grade of steel required, and the grade is predominantly expressed in terms of the yield strength. That is generally a figure way beyond anything it will experience in a boat.

 

Modern steels are finer grained and harder than earlier steels and due to improvements in production methods will be largely free of inclusions and hydrogen bubbles which steels of 50 years vintage are likely to be riddled with. As the owner of a 1968 boat I can confirm the steel rusts well enough and won't be as good a product as a modern steel from anywhere in the world in terms of its engineering capabilities. But in a canal boat it matters not a jot. In my work - which involves assurance of steel components - I would be very wary of 1968 steel in some applications and not just because it's old.

 

Going back to those surveys don't they both measure the bottom at 10mm and the sides at 6mm? The other stuff is noise. Quoting steel thicknesses to tenths of millimetres is also nonsense when the method has little to no repeatability or reliability and you don't have a reference set of thickness from new (because a nominal 10mm plate will not uniformly be 10.0mm throughout if indeed it is even that thick at any one place).

 

As others have said the only thing that matters is independently verifying the condition for yourself.

 

Thank you, this is very useful and well informed. Are you saying because the thickness is as about as it should be enough it's fine? Is pitting not likely to get worse where it's bad already, and widespread pitting potentially costly to rectify?

[blackrose]

10 hours ago, Slow and Steady said:

ref cars and old steel I have experience here and sorry but it's true certainly regarding old Volkswagons from the 60's compared to the 70's. The older stuff is like rock and does not warp (shrink/expand) to anywhere near the extant the more modern stuff does. There are quite a few restorers who specialise in old VW vans and some of them will only work on the older ones for this reason. Roll on a few more decades and pattern part body panels - so weak and bendy you wonder if they are made from lead sheet! This probably doesn't apply to stock sheet steel boats are made from, but the quality of steel CHOSEN by some car makers is by no means a constant thing.

 

I used to make some panels from old stock steel shelving after acquiring a heap of it and it was like magic. Without a doubt it corroded much more slowly than more modern steel sheet and this was just shelving, nothing special. There are sooo many different types of steel and steel used to be cheap enough that better quality recipes were used.

 

Check this out - the shiny bright bit and the rusty bit were both cleaned up at the same time and left a couple of days.

The shiny is ex 1940s/50s shelving below the weld, 1968 above, the rusty is 2010 sheet steel.

 

Are you sure the old panels aren't just thicker gauge steel?

[DShK]

12 hours ago, Mike Tee said:

From looking at the boat, the forward bilge was because the well deck was basically at the same level as the interior of the boat, and could not, like is usual, drain overboard. Not a design I particularly like, which is why I didn't go look at it myself! As it turned out, we found something better for us.

Ah that's an interesting point, I hadn't thought of the draining part. I really liked the well deck being low as it sort of made it into an extension of the living area. But this is a really good point that I totally missed. I wonder how it drained?

[Captain Pegg]

41 minutes ago, DShK said:

Thank you, this is very useful and well informed. Are you saying because the thickness is as about as it should be enough it's fine? Is pitting not likely to get worse where it's bad already, and widespread pitting potentially costly to rectify?

I’m saying that whatever is observed is highly unlikely to be a product of the steel used and that the survey outputs suggest the hull is basically sound.

 

However the general description you give and the fact that one surveyor observed widespread corrosion along the waterline suggest this boat may not have been particularly well maintained and may not have been subject to routine blacking that would largely prevent widespread corrosion along the waterline. Observation of corrosion on the surface of poorly coated steel is to be expected but it doesn’t mean the steel is unduly compromised. A lot of rust results from very little parent steel.

I do wonder if surveyors have any consistency in what they describe as pitting. It would be interesting to see what constitutes a 1mm pit.

 

If you are interested in this boat your own observations and those of your own surveyor are important and much more relevant than those of the seller or any old survey. Have a look for distinct small spots of deep corrosion where the depth is clearly significant in relation to the width. That’s a pit and they aren’t a natural product of rusting. Rusting results in lamination and when broken off leaves a mottled surface that will be familiar to anyone who has ever cleaned up an old baseplate. That shouldn’t be mistaken for pitting.

[Alan de Enfield]

21 hours ago, DShK said:

Move forward to viewing the boat. The owner had relocated so his neighbour let me on the boat at it's mooring. Helpfully the owner had left paperwork for me to view. In it I found a survey from 2016, which was considerably different to the one I had seen before. While the bottom had minimal corrosion, the sides had "widespread pitting corrosion" between 1-2mm (measured thickness 5.6-6.7mm). Moderate and heavy wastage corrosion around the waterline. The difference between these two surveys, and the advert claim, raised huge red flags.

 

What was the time period between surveys ?

One was 2016, and presumably the 'recent survey' would be in the last couple of years.

 

A member on this forum had his boat go from 6mm to under 2mm in 18 months - it may not be common but it is also not unknown.

 

There are several types of corrosion and many reasons why a boat starts, or suffers from increased, rates of corrosion.

 

It can be 'self inflicted' (a wiring problem on your boat), it can be that you are moored near a boat with an electrical problem, it can be that if 'hooked up' to the mains you have common earth with other boats, it can that Microbial corroion has infected your hull (mainly if you moor in nitrogen rich waters (rural areas) or contaminated mud areas).

 

It is not a simple subject with no one answer.

[Captain Pegg]

1 hour ago, blackrose said:

 

Are you sure the old panels aren't just thicker gauge steel?

That thought crossed my mind because of course if you can produce a more reliable product you can make it thinner. However it seemed a bit obvious.

 

What would make a difference is if the two panels had been subject to different amounts of cold working.

 

But without knowing they are actually the same grade of material any comparison is pretty meaningless.

[Mad Harold]

You probably won't get the same hull thickness readings twice,because of a different surveyor and perhaps different equipment.

Have used an ultrasonic thickness tester ( not on boats) and before use the instrument I had,had to be calibrated.

This was simply measuring the thickness of a known piece of metal, and adjusting the reading to the known test piece.If this was not done the readings were all over the place.

I veture to suggest that the member's boat that went from 6mm to 2mm in a short time, could be due to faulty equipment and/or human error.

To lose 4mm of metal in 18 months seems to me unlikely (even if the boat was floating in battery acid!) One of he thickness reports could be somewhere near, but surely not both.

 

[MtB]

45 minutes ago, Captain Pegg said:

Have a look for distinct small spots of deep corrosion where the depth is clearly significant in relation to the width. That’s a pit and they aren’t a natural product of rusting. Rusting results in lamination and when broken off leaves a mottled surface that will be familiar to anyone who has ever cleaned up an old baseplate. That shouldn’t be mistaken for pitting.

 

There is a whole other dimension to surveyors' comments on corrosion, barely been touched on so far in this thread. Insurance. There are two reasons for getting a survey and while boat buyers often think they are employing a surveyor to produce a condition report for their information, the surveyor sometimes seems to think they are working for the insurance companies and are being employed to protect the interests of the insurers. Hence the astoundingly conservative advice one sometimes reads about where some 2mm pitting on an elderly boat has resulted in a survey report recommending whole extra skin of 5mm thick steel is added to the hull. A grossly unnecessary recommendation from a practical point of view in my opinion, but necessary given insurance firms generally demand a minimum hull thickness of 4mm as a condition of offering comprehensive insurance.

 

So when a survey report comes back baldly stating 5mm overplating below the waterline is required, I think it is well worth enquiring why. The buyer might, like me, take the view that a 30 year old boat is two thirds of its way to the end of its life and so what if it can only be insured third party? What are the risks of it sinking from some 2mm pitting in 6mm steel after 30 years? Approaching zero in my opinion, although yours might be different.

 

The main reasons for boats sinking are skipper error in a lock (i.e. not corrosion) and some sort of mis-management of the boat i.e. leaving a weed hatch off or a coolant hose splitting. I can't think of a single incident ever, of a steel NB unexpectedly and spontaneously sinking from corrosion. Consequently I'm happy to take the risk and take extra care not to sink my own boat.

 

 

Edited March 20, 2022 by MtB

[haggis]

49 minutes ago, DShK said:

Ah that's an interesting point, I hadn't thought of the draining part. I really liked the well deck being low as it sort of made it into an extension of the living area. But this is a really good point that I totally missed. I wonder how it drained?

When the front deck is lower than the water level, I think the usual method of draining it was a pipe which ran under the floor of the cabin into the engine bilge. I gather that this pipe was prone to corrosion but being under the floor was not easy to access and check/repair and the result would be water under the floor boards. Having a front cratch cover would be a great help as it would eliminate the water getting onto the front deck. 

 

Edited March 20, 2022 by haggis

[Alan de Enfield]

34 minutes ago, Mad Harold said:

You probably won't get the same hull thickness readings twice,because of a different surveyor and perhaps different equipment.

Have used an ultrasonic thickness tester ( not on boats) and before use the instrument I had,had to be calibrated.

This was simply measuring the thickness of a known piece of metal, and adjusting the reading to the known test piece.If this was not done the readings were all over the place.

I veture to suggest that the member's boat that went from 6mm to 2mm in a short time, could be due to faulty equipment and/or human error.

To lose 4mm of metal in 18 months seems to me unlikely (even if the boat was floating in battery acid!) One of he thickness reports could be somewhere near, but surely not both.

 

 

I'm sure @Keeping Up wouldn't agree with you - let him tell you his story.

 

It is easy enough to dismiss it as operator error, but how many oprators are needed to get the same result before it is accepted as fact ?

Edited March 20, 2022 by Alan de Enfield

[MtB]

10 minutes ago, Alan de Enfield said:

 

I'm sure @Keeping Up wouldn't agree with you - let him tell you his story.

 

It is easy enough to dismiss it as operator error, but how many oprators are needed to get the same result before it is accepted as fact ?

 

 

So are you saying you think Keeping Up's boat which was fine for 20 years then suddenly corroded down to 2mm in a year or two, was caused by the original metal quality not some sort of electrical problem?

 

That nice Mr Occam applying his handy razor would suggest otherwise. 

 

https://en.wikipedia.org/wiki/Occam's_razor

[roland elsdon]

32 minutes ago, MtB said:

 

There is a whole other dimension to surveyors' comments on corrosion, barely been touched on so far in this thread. Insurance. There are two reasons for getting a survey and while boat buyers often think they are employing a surveyor to produce a condition report for their information, the surveyor sometimes seems to think they are working for the insurance companies and are being employed to protect the interests of the insurers. Hence the astoundingly conservative advice one sometimes reads about where some 2mm pitting on an elderly boat has resulted in a survey report recommending whole extra skin of 5mm thick steel is added to the hull. A grossly unnecessary recommendation from a practical point of view in my opinion, but necessary given insurance firms generally demand a minimum hull thickness of 4mm as a condition of offering comprehensive insurance.

 

So when a survey report comes back baldly stating 5mm overplating below the waterline is required, I think it is well worth enquiring why. The buyer might, like me, take the view that a 30 year old boat is two thirds of its way to the end of its life and so what if it can only be insured third party? What are the risks of it sinking from some 2mm pitting in 6mm steel after 30 years? Approaching zero in my opinion, although yours might be different.

 

The main reasons for boats sinking are skipper error in a lock (i.e. not corrosion) and some sort of mis-management of the boat i.e. leaving a weed hatch off or a coolant hose splitting. I can't think of a single incident ever, of a steel NB unexpectedly and spontaneously sinking from corrosion. Consequently I'm happy to take the risk and take extra care not to sink my own boat.

 

 

I knocked two holes in Atalanta her 1948 refooting having only lasted to 1994Original footings from 1935 having been replaced by riveted section after only 13 years.

Of course she was composite and working, so full of damp crap below the shuts.

 

The first hole was my own fault, working under the waterline ( following a good survey)😭 I blew a hole while welding. A few knee patches  every docking kept her going and going.

The second hole was going in to top lock of Stockton in 1993  breasted catching the iron work and knocking a hole. A bolt and penny washers kept her up until 1994.

 

By 1994 when refooted  and bottomed she was like lace. 
 

In my experience you get damp spots and weeps rather than great gushers. We had two good bilge pumps one on each side of the Kelson, and a spare with the float set higher. They coped with various leaks ( composite bottoms) and gave plenty of warning of issues.

insurance companies will not pay out if your boat sinks through a hole caused by corrosion. That’s failure to maintain. However the 4 mm thing is to protect against something like grinding over a safe , ford sierra , or girder and holing your boat.

, which is an insurance event.

[Alan de Enfield]

12 minutes ago, MtB said:

So are you saying you think Keeping Up's boat which was fine for 20 years then suddenly corroded down to 2mm in a year or two, was caused by the original metal quality not some sort of electrical problem?

 

That nice Mr Occam applying his handy razor would suggest otherwise. 

 

There you go again - jumping to conclusions and putting words into people mouths.

 

The thread is about the corrosion differences reported in two surveys several years apart - maybe you missed this bit because you thought 'here is something I can 'jump-on' and didn't read any further .....................

 

 

1 hour ago, Alan de Enfield said:

There are several types of corrosion and many reasons why a boat starts, or suffers from increased, rates of corrosion.

 

It can be 'self inflicted' (a wiring problem on your boat), it can be that you are moored near a boat with an electrical problem, it can be that if 'hooked up' to the mains you have common earth with other boats, it can that Microbial corroion has infected your hull (mainly if you moor in nitrogen rich waters (rural areas) or contaminated mud areas).

 

It is not a simple subject with no one answer.

 

[MtB]

8 minutes ago, Alan de Enfield said:

There you go again - jumping to conclusions and putting words into people mouths.

 

 

Nope, it was a question (not a putting of words in people's mouths) because I was trying to find out what you thought on the subject.

 

I notice you swerved answering with your little rant. 

 

 

[Alan de Enfield]

4 minutes ago, MtB said:

 

 

Nope, it was a question (not a putting of words in people's mouths) because I was trying to find out what you thought on the subject.

 

I notice you swerved answering with your little rant. 

 

 

 

 

I posted what I thought on the subject.

If you would like my thoughts on steel variances - "I have no knowledge on any changes in chemical composition of steels in the last century - only what I read".

 

My comments were based on corrosion by other methods than simple rusting.

Of which there are several, many not understood, or never identified.

[DShK]

I'd like to just reiterate that the worse of the two reports was the earlier one in 2016. The better sounding report, which was done for insurance purposes, was done in 2021. So this isn't a case of the boat suddenly getting worse. Quite the opposite! And seems to be down to the difference of opinion (context perhaps important perhaps?) of the surveyor.