Millscale

[rider66]

Seems that this is quite a topic.

 

1) how many builders actually bother to get it off/ source scale free steel

 

2) I'm considering a new-build that seems to suffer from it. Do I have any re-course to the builder? Surely trade discription should cover anything not fit for purpose.

 

3) Does it really cause the paint to fall off

 

4) Does anyone know a good 2k/twin pack product/supplier

[Gary Peacock]

A bit of an interesting one this one.

 

If you were to follow the BMF guidance and steel suppliers guidance removing mill scale at a minimum for weld preparation is a must using fully descaled plate would be good practise.

 

The problem is down to cost it probably adds £500.00 or so to the cost of an hull so many don't.

 

Builders who use large plates can't because plates that large can't or would be ridiculously more expensive to get done so many of the bulk manufactures who use larger plates to speed production can't offer it.

 

We have always used descaled and oiled plate because it is easier to work with and finish but we obviously pass the cost on.

 

The two proper alternatives are the old practise of letting the completed hull rust and then shot blast the rust away or more time consumingly to shot blast the completed hull to remove the scale directly both of which add cost.

 

The third very popular route is to just paint it and cross your fingers the scale doesn't decide to fall off bringing the paint with it.

[RLWP]

Seems that this is quite a topic.

 

1) how many builders actually bother to get it off/ source scale free steel

 

2) I'm considering a new-build that seems to suffer from it. Do I have any re-course to the builder? Surely trade discription should cover anything not fit for purpose.

 

3) Does it really cause the paint to fall off

 

4) Does anyone know a good 2k/twin pack product/supplier

 

Hi Rider,

 

how can you tell that the boat is suffering from millscale? I don't have any experience of this and I am curious to know how millscale shows itself on a boat.

 

Richard

[rider66]

A bit of an interesting one this one.

 

If you were to follow the BMF guidance and steel suppliers guidance removing mill scale at a minimum for weld preparation is a must using fully descaled plate would be good practise.

 

The problem is down to cost it probably adds £500.00 or so to the cost of an hull so many don't.

 

Builders who use large plates can't because plates that large can't or would be ridiculously more expensive to get done so many of the bulk manufactures who use larger plates to speed production can't offer it.

 

We have always used descaled and oiled plate because it is easier to work with and finish but we obviously pass the cost on.

 

The two proper alternatives are the old practise of letting the completed hull rust and then shot blast the rust away or more time consumingly to shot blast the completed hull to remove the scale directly both of which add cost.

 

The third very popular route is to just paint it and cross your fingers the scale doesn't decide to fall off bringing the paint with it.

 

 

A bit of an interesting one this one.

 

If you were to follow the BMF guidance and steel suppliers guidance removing mill scale at a minimum for weld preparation is a must using fully descaled plate would be good practise.

 

The problem is down to cost it probably adds £500.00 or so to the cost of an hull so many don't.

 

Builders who use large plates can't because plates that large can't or would be ridiculously more expensive to get done so many of the bulk manufactures who use larger plates to speed production can't offer it.

 

We have always used descaled and oiled plate because it is easier to work with and finish but we obviously pass the cost on.

 

The two proper alternatives are the old practise of letting the completed hull rust and then shot blast the rust away or more time consumingly to shot blast the completed hull to remove the scale directly both of which add cost.

 

The third very popular route is to just paint it and cross your fingers the scale doesn't decide to fall off bringing the paint with it.

 

Think I'll bite the bullet and go for the blasting option seeing as she's not yet been in the water but has had the hull painted. Pity really as she's been on land for 3 years so left unpainted, it would rust and fall off.

 

 

Hi Rider,

 

how can you tell that the boat is suffering from millscale? I don't have any experience of this and I am curious to know how millscale shows itself on a boat.

 

Richard

 

I have very little experience. The surveyor pointed it out. It seems to be a rough coating on the steel. It can be square feet sized. There are photos of it on other posts

[Gary Peacock]

This will give you some idea descaled steel is bright with no rust or scale. The scale is removed by acid and the sheets are then coated with a protective oil before they leave the steel mill.

 

 

The picture below show a hull being built from descaled and oiled steel next door.

 

 

The next picture shows a sheet of descaled and oiled 6mm sheet laid on top of a mill scaled 6mm sheet you can see that it is black. (That is the scale.)

 

 

 

 

The last two pictures show a Heron boat with some of the primer removed the black patches are also scale.

 

 

 

These were discovered after the primer and scale started to come away.

 

There is no reason other than the cost saving to work with scaled steel!

[Chris Pink]

Think I'll bite the bullet and go for the blasting option seeing as she's not yet been in the water but has had the hull painted. Pity really as she's been on land for 3 years so left unpainted, it would rust and fall off.

 

Well if the paint is still on there after 3 years i would leave it alone.

 

epoxy coatings are not generally recommended for canal use, the supplier i spoke to said only use it if you don't go anywhere or are on the sea, it chips real easy.

 

 

"how can you tell that the boat is suffering from millscale? I don't have any experience of this and I am curious to know how millscale shows itself on a boat."

 

It is a black coating on top of the steel, so you will have 3 states or finish on bare steel; bright, rusty and scale.

[rider66]

A bit of an interesting one this one.

 

If you were to follow the BMF guidance and steel suppliers guidance removing mill scale at a minimum for weld preparation is a must using fully descaled plate would be good practise.

 

The problem is down to cost it probably adds £500.00 or so to the cost of an hull so many don't.

 

Builders who use large plates can't because plates that large can't or would be ridiculously more expensive to get done so many of the bulk manufactures who use larger plates to speed production can't offer it.

 

We have always used descaled and oiled plate because it is easier to work with and finish but we obviously pass the cost on.

 

The two proper alternatives are the old practise of letting the completed hull rust and then shot blast the rust away or more time consumingly to shot blast the completed hull to remove the scale directly both of which add cost.

 

The third very popular route is to just paint it and cross your fingers the scale doesn't decide to fall off bringing the paint with it.

 

I see from previous posts, you have moved away from 2 pack for the hull. Was that onto scale free steel. Is it really not worth the cost?

[blackrose]

I didn't realise millscale cold be classified as equipment but anyway, when you come to black your boat it's quite obvious if millscale is present. It sort of looks like limescale on the inside of a kettle, only it isn't white and it's harder. Some 15 year old hulls still have millscale firmly bonded to them, so it's not something to worry about too much as long as your boat comes out the water every few years.

[RLWP]

This will give you some idea descaled steel is bright with no rust or scale. The scale is removed by acid and the sheets are then coated with a protective oil before they leave the steel mill.

 

The next picture shows a sheet of descaled and oiled 6mm sheet laid on top of a mill scaled 6mm sheet you can see that it is black. (That is the scale.)

 

These were discovered after the primer and scale started to come away.

 

There is no reason other than the cost saving to work with scaled steel!

 

So, with my engineers hat on then (blimey it still fits!) the mill scaled stuff is plain black hot rolled sheet, what you are using is the same but acid treated to remove the black surface. This leaves a surface that is bright like BDMS (Bright Drawn Mild Steel). The black scale is prone to separating from the base metal and can flake off taking the paint with it.

 

Is this millscale a sheet metal thing as it doesn't seem to be present on plain black bar?

 

Does the flaking show up more where the sheet has been "worked" such as at the bow and stern?

 

Richard

 

Learning all the time.....

[Chris Pink]

it doesn't seem to be present on plain black bar?

 

hmmm, the clue is the word 'black'

 

and yes bending and working makes the scales crack it is not malleable like the steel.

[RLWP]

hmmm, the clue is the word 'black'

 

and yes bending and working makes the scales crack it is not malleable like the steel.

 

Well, yes, but the surface isn't usually covered in large scales, just a fine black granular looking finish. Having done some smithing I know that you can generate quite impressive scales fairly easily but these can be brushed off when hot. You still have black steel though.

 

Richard

[John Orentas]

Grit blasting a boat after manufacture is not usually an option these days, the process is so noisy and messy few boatyards or dock owners will allow it on their sites.. The best way, if not entirely realistic is the old way of leaving your unpainted shell out in the rain for a few years and then attacking it with an angle grinder.

 

Surely the best way is Gary's method of using pre-prepared steel for the build.

 

Don't exaggerate this issue though, there are thousands of 20+ year old boats out there that have been painted on top of the scale, and you would never know.

[rider66]

Grit blasting a boat after manufacture is not usually an option these days, the process is so noisy and messy few boatyards or dock owners will allow it on their sites.. The best way, if not entirely realistic is the old way of leaving your unpainted shell out in the rain for a few years and then attacking it with an angle grinder.

 

Surely the best way is Gary's method of using pre-prepared steel for the build.

 

Don't exaggerate this issue though, there are thousands of 20+ year old boats out there that have been painted on top of the scale, and you would never know.

I'm sure Gary's way is the best and I don't have 3 years to leave the shell out of the water. It's rather a pity that the current owner didn't know this and painted it and then left it out.

It would be convenient if I was just being hysterical, but as this will be my floating home I want to try to get it right. Hence questions about bottom blacking.

[Chris Pink]

Well, yes, but the surface isn't usually covered in large scales, just a fine black granular looking finish.

 

yes, that is (mill)scale), pure steel is shiny bright.

[RLWP]

I'm considering a new-build that seems to suffer from it.

 

Hi Rider,

 

if this really is a new build and the mill scale bothers you, don't buy it. There will be other boats.

 

Richard

[rider66]

Hi Rider,

 

if this really is a new build and the mill scale bothers you, don't buy it. There will be other boats.

 

Richard

It really is a new build. I must admit I had never heard of millscale until the surveyor mentioned it. It seems it doesn't bother most people/most people have never heard of it.

[Gary Peacock]

It really is a new build. I must admit I had never heard of millscale until the surveyor mentioned it. It seems it doesn't bother most people/most people have never heard of it.

 

The big problem with mill scale is that it is unpredictable it can stay stuck for years and never move or it can cause problems quickly.

 

Many people will not have a herd of it even though many of the biggest boatbuilders hulls were covered in it, but you have to understand that boatbuilders only tell you what is good they seldom mention steel specs, welding methods, scantling calculation, RCD compliance, documentation and a lot of other similar things because all these add costs without any visual indicators. These kind of things either increase the overall cost of the boat and reduce profits or make them more expensive so less competitive in a very competitive market.

 

So the bitter pill is it really comes down to the customer (and boaters are well known to be very easy to part from their money) to ask questions and confirm the boatbuilders answers.

 

Millscale isn't the end of the world but being armed with knowledge of it and other things is very handy when needing to cut through the boatbuilders sales pitch.

 

I looked at a near new boat yesterday that was in the top five worst boats I have ever seen ranking, the owners were giving the potential purchases surveyor loads of stick because he pointed out a host of problems that were going to seriously effect the price they had more or less got a guaranteed sale for. (He was only doing the job he was being paid to do.)

 

Now I would like to bet that they never questioned the boatbuilders practises or even wondered how the builder built boats for the price he did.

 

But the poor surveyor really spoilt their plans for them and they thought it wall all his fault!

[rider66]

The big problem with mill scale is that it is unpredictable it can stay stuck for years and never move or it can cause problems quickly.

 

Many people will not have a herd of it even though many of the biggest boatbuilders hulls were covered in it, but you have to understand that boatbuilders only tell you what is good they seldom mention steel specs, welding methods, scantling calculation, RCD compliance, documentation and a lot of other similar things because all these add costs without any visual indicators. These kind of things either increase the overall cost of the boat and reduce profits or make them more expensive so less competitive in a very competitive market.

 

So the bitter pill is it really comes down to the customer (and boaters are well known to be very easy to part from their money) to ask questions and confirm the boatbuilders answers.

 

Millscale isn't the end of the world but being armed with knowledge of it and other things is very handy when needing to cut through the boatbuilders sales pitch.

 

I looked at a near new boat yesterday that was in the top five worst boats I have ever seen ranking, the owners were giving the potential purchases surveyor loads of stick because he pointed out a host of problems that were going to seriously effect the price they had more or less got a guaranteed sale for. (He was only doing the job he was being paid to do.)

 

Now I would like to bet that they never questioned the boatbuilders practises or even wondered how the builder built boats for the price he did.

 

But the poor surveyor really spoilt their plans for them and they thought it wall all his fault!

Thank you. Must admit that the surveyor was worth his weight in gold. I assume that if the scale moves I would have to get the boat out of the water and do what I could do now but for alot more money. Am I safe to assume that just because it hasn't moved on a boat that hasn't been in the water, there's no telling what it might do once immersed?

[Gary Peacock]

Thank you. Must admit that the surveyor was worth his weight in gold. I assume that if the scale moves I would have to get the boat out of the water and do what I could do now but for alot more money. Am I safe to assume that just because it hasn't moved on a boat that hasn't been in the water, there's no telling what it might do once immersed?

 

I think at the point you are at now to get rid of the scale without the builder is going to very helpful is going to be very difficult. I would be tempted to keep your fingers crossed and and risk it, lots of boats will have millscale under the blacking and paint and the owners will not even realise.

 

You will have to consider how the builder operates if they are at the pricey prestigious end of the market I would stand my ground and try and come to an arrangement to both meet the cost, if they are one of the cheaper budget shell builders then they probably don't even think twice about millscale without descaled steel was requested before the build.

 

I have only known of one real disaster involving paint and scale on a new boat so it can't be such a common cause of problems.

[rider66]

I think at the point you are at now to get rid of the scale without the builder is going to very helpful is going to be very difficult. I would be tempted to keep your fingers crossed and and risk it, lots of boats will have millscale under the blacking and paint and the owners will not even realise.

 

You will have to consider how the builder operates if they are at the pricey prestigious end of the market I would stand my ground and try and come to an arrangement to both meet the cost, if they are one of the cheaper budget shell builders then they probably don't even think twice about millscale without descaled steel was requested before the build.

 

I have only known of one real disaster involving paint and scale on a new boat so it can't be such a common cause of problems.

Hmm. Further complicated by the fact that its not coming direct from builders. A well known Merseyside company sold it to the current owner as a sailaway 3 years ago. Managed to source a blasting firm that will blast and prime where it is and also permission to do the work where the boat stands. Still, with epoxy paint it will be best part of £2500. More if I want the base plate doing too.

[RLWP]

Hmm. Further complicated by the fact that its not coming direct from builders. A well known Merseyside company sold it to the current owner as a sailaway 3 years ago. Managed to source a blasting firm that will blast and prime where it is and also permission to do the work where the boat stands. Still, with epoxy paint it will be best part of £2500. More if I want the base plate doing too.

 

So I think you have several options here.

 

It is a second hand boat so if the millscale bothers you, walk away.

 

Get £2500 knocked off the price and get the work done

 

Pay for the work to be done yourself

 

Take Gary's advice and wait and see what happens

 

Get £2500 knocked of the price then take Gary's advice and wait and see what happens.

 

I would take the last option in the above list....

 

Richard

 

I'll bet that our 20 year old boat didn't have acid treated steel.....

[Gary Peacock]

Hmm. Further complicated by the fact that its not coming direct from builders. A well known Merseyside company sold it to the current owner as a sailaway 3 years ago. Managed to source a blasting firm that will blast and prime where it is and also permission to do the work where the boat stands. Still, with epoxy paint it will be best part of £2500. More if I want the base plate doing too.

 

In that case it is also worth asking the question is the boat now CE marked?

 

Because if not they are breaking the law selling it. (If it isn't that could give you a bargaining chip on price that little bit of information if you promise not to tell Trading Standards !)

[rider66]

So I think you have several options here.

 

It is a second hand boat so if the millscale bothers you, walk away.

 

Get £2500 knocked off the price and get the work done

 

Pay for the work to be done yourself

 

Take Gary's advice and wait and see what happens

 

Get £2500 knocked of the price then take Gary's advice and wait and see what happens.

 

I would take the last option in the above list....

 

Richard

 

I'll bet that our 20 year old boat didn't have acid treated steel.....

I'll bet it didn't and I'll bet its still floating. Yes, the last option sounds the most attractive. Money in the bank as it were. And of course, I wouldn't spend it. Tricky tho as the work was to be done where the boat presently lives

Christian

[RLWP]

I'll bet it didn't and I'll bet its still floating. Yes, the last option sounds the most attractive. Money in the bank as it were. And of course, I wouldn't spend it. Tricky tho as the work was to be done where the boat presently lives

Christian

 

You are going to have to get the hull blacked again sometime in the next 2-3 years anyway.

 

Richard

[rider66]

In that case it is also worth asking the question is the boat now CE marked?

 

Because if not they are breaking the law selling it. (If it isn't that could give you a bargaining chip on price that little bit of information if you promise not to tell Trading Standards !)

 

No its not CE marked-thats the European thingy?. I understiood from the surveyor that he can sell it on and I'll have to get it done within 5 years of "finishing" the boat. Another £2000 for CE i believe.

 

Christian

 

 

You are going to have to get the hull blacked again sometime in the next 2-3 years anyway.

 

Richard

True. Unless I epoxy it