Blacking paint recommendations

[Sea Dog]

When I bought my boat it was blacked with Intertuf 16 which is bituminous. Since then I've used Rylards with no adverse reaction. As Tony says, the number after Intertuf is important although it may likely enough be 16 if it's common blacking. A diesel damped rag will turn black on bitumen iirc. Incidentally,  Rylards Premium is thinner so penetrates well, is shiny and slightly more diesel resistant than other bitumen. Rytex is thicker and a more matte finish. Folk often use a combination of coats using the two.

[matty40s]

4 hours ago, 13-10 said:

Thanks Tony will follow the advice from yourself and others on here. Have to say if the bumf about Keelblack is correct I'm tempted to use it

The bumph they sold it on to start of with is incorrect. They sold it on reducing dock times and you can put it on when wet. 

It was only later when disgruntled customers went direct to Fertans manufacturers for more information that it was discovered that much longer times are required if using Fertan than originally specified, and also that curing time before going back in the water was also extended. 

Therefore not reducing dock times.

 

[dmr]

This Keelblack sounds like really good stuff as long as you do lots of preparation and don't put it onto a bare metal hull. It appears to need a lot of drying too. I think for best results I would book the dock for two weeks, shot blast, put a couple of coats of two pack on, then put as many coats of KeelBlack on as time and budget allows.

If time is tight then maybe skip the Keelblack.

..............Dave

[13-10]

11 hours ago, matty40s said:

The bumph they sold it on to start of with is incorrect. They sold it on reducing dock times and you can put it on when wet. 

It was only later when disgruntled customers went direct to Fertans manufacturers for more information that it was discovered that much longer times are required if using Fertan than originally specified, and also that curing time before going back in the water was also extended. 

Therefore not reducing dock times.

 

The website quotes 24 hours for the Fertan to work and allow 48hrs for the Keelblack to cure. It says allow 4-5 days dock time, is that about right or are they still being optimistic

I'm going to book a dry dock for a week so think I'll have enough time for either that or traditional blacking

[rusty69]

7 minutes ago, 13-10 said:

I'm going to book a dry dock for a week so think I'll have enough time for either that or traditional blacking

Depends if it's a covered dry dock you are booking. 

We blacked our 70ft boat (two of us) in summer this year, the first three day, no work took place as it rained non stop (only a slight exaggeration) 

[Dr Bob]

You should be ok for a week but do it as late in April as you can as the temperatures tend to be much lower than down here. Plan to paint in the afternoon so you are well above the dew point after the steel has warmed a bit. Fertan can be used over damp surfaces and best not put on in the hot sun, unlikely up your way in April, so best put on early morning.

I would wait till May/ June.

[matty40s]

The website is still incorrect then .

The Fertan 24 hours curing time is temperature dependant,  it is longer at lower temperatures. The hull must also he dry to use Fertan effectively. 

48 hours curing time for keelblack. 

That gives you exactly how much spare time in 4- 5 docking days to empty dock, pressure wash, dry hull, apply several coats, refloat.  

Do the maths.

Edited November 25, 2017 by matty40s

[GUMPY]

Mine was in on a Saturday morning, finished by Wednesday night, water back in dock overnight Friday. Where the time saving does occur is that by the time you have been round the boat and finished one coat you can start the next one immediately rather than having to wait 24hrs so 4 coats in a day is easily doable.

[matty40s]

29 minutes ago, Loddon said:

Mine was in on a Saturday morning, finished by Wednesday night, water back in dock overnight Friday. Where the time saving does occur is that by the time you have been round the boat and finished one coat you can start the next one immediately rather than having to wait 24hrs so 4 coats in a day is easily doable.

so yours was done at the warmest time of year and still 7 days.

[GUMPY]

1 minute ago, matty40s said:

so yours was done at the warmest time of year and still 7 days.

And how long to get 3 coats of bitumen on? More than that if drying times adhered to. Normal stuff should be left overnight before recoating and 36-48 hrs to dry before wetting.

I don't care anyway for me keelblack was an easy option.

[peterboat]

5 minutes ago, Loddon said:

And how long to get 3 coats of bitumen on? More than that if drying times adhered to. Normal stuff should be left overnight before recoating and 36-48 hrs to dry before wetting.

I don't care anyway for me keelblack was an easy option.

Mine is due out next year in July with Johns boat mine was covering Zinger blacking his was very rusty so fertan was used. So we will see how good it is after two years on two very different surfaces wont we? We followed the instructions to the letter and if I am honest I have never had anything as easy to apply as keelblack, on Johns boat it went into the pitting whereas normal blacking just seals it over unless you thin it out. I will be ordering the sprayable version next year as we have that option open to us, looking at what I can see on my boat it is still well covered other than where I have removed it by hitting things but thats what happens in boating isnt it?

[matty40s]

57 minutes ago, Loddon said:

And how long to get 3 coats of bitumen on? More than that if drying times adhered to. Normal stuff should be left overnight before recoating and 36-48 hrs to dry before wetting.

I don't care anyway for me keelblack was an easy option.

Bitumen isn' claiming to reduce docking times to 4 or 5 days.

[rgreg]

I used to undercoat the blacking with Red Oxide but found the adhesion between the two to be worse than when the bitumen is painted directly onto the metal. The Red Oxide sticks well to the hull and withstands a lot of scrapes but I now don't use it due to the blacking adhesion issue. The blacking I use is one coat of Rylards Premium followed by two coats of Rylards Rytex which was a combination recommended to me by an old hand several years ago.

[Sea Dog]

2 hours ago, peterboat said:

....  it went into the pitting whereas normal blacking just seals it over unless you thin it out.

^^^^ This is why this... 

2 minutes ago, rgreg said:

The blacking I use is one coat of Rylards Premium followed by two coats of Rylards Rytex which was a combination recommended to me by an old hand several years ago.

....is a good idea in my book.

[peterboat]

22 hours ago, matty40s said:

Bitumen isn' claiming to reduce docking times to 4 or 5 days.

The thing is matty you can do it in 4 -5 days, out and powerwashed, if it has no rust at waterline bang 3 coats of keelblack on one after other, 48 hours later back in no probs.

If rusty fertan 24 hours later powerwash off and 3 coats of keelback one after other 48 hours later back in

[Bloomsberry]

I did mine in interzone954 after a number of very dissappointing results using bitumen, it's evil stuff and even cures underwater.

The surface has to be prepared down to bare metal using a rotary blaster or similar, very time consuming.

In 3 days I only had time to do the waterline, weld seams and pitted areas .

It was done 16 months ago and is still intact with no trace of any failure.

It's coming out again next year to inspect it more closely and tidy up any dodgy areas and treat areas that weren't got to the last time.

[ditchcrawler]

On 24/11/2017 at 22:24, dmr said:

This Keelblack sounds like really good stuff as long as you do lots of preparation and don't put it onto a bare metal hull. It appears to need a lot of drying too. I think for best results I would book the dock for two weeks, shot blast, put a couple of coats of two pack on, then put as many coats of KeelBlack on as time and budget allows.

If time is tight then maybe skip the Keelblack.

..............Dave

I think I go with the last line

 

[cuthound]

10 hours ago, Bloomsberry said:

I did mine in interzone954 after a number of very dissappointing results using bitumen, it's evil stuff and even cures underwater.

The surface has to be prepared down to bare metal using a rotary blaster or similar, very time consuming.

In 3 days I only had time to do the waterline, weld seams and pitted areas .

It was done 16 months ago and is still intact with no trace of any failure.

It's coming out again next year to inspect it more closely and tidy up any dodgy areas and treat areas that weren't got to the last time.

My boat had Intertuff 954 over Zinga from new. 

I had her docked in May (it has been docked every 3-5 years but never reblacked from new) and was told that under the waterline the blacking was still good, above the waterline were just a few chips and scrapes, so to leave it for another coupme of years and then dock again.

[jenevers]

So what happens if your boat goes back in the water before the bitumen is fully dried?

Is bitumen soluble in water? If not, does it just remain soft? And if so, is it any less protective then dried bitumen when the hull scrapes against a rock?

[Tim Lewis]

On 11/25/2017 at 14:11, rgreg said:

I used to undercoat the blacking with Red Oxide but found the adhesion between the two to be worse than when the bitumen is painted directly onto the metal. The Red Oxide sticks well to the hull and withstands a lot of scrapes but I now don't use it due to the blacking adhesion issue. The blacking I use is one coat of Rylards Premium followed by two coats of Rylards Rytex which was a combination recommended to me by an old hand several years ago.

We start with the premium as being thinner that the Rytex it is easier to brush into the pits. We then second coat with Rytex but use premium for the third coat as it gives a shinier finish.

Tim

[Dr Bob]

1 hour ago, jenevers said:

So what happens if your boat goes back in the water before the bitumen is fully dried?

Is bitumen soluble in water? If not, does it just remain soft? And if so, is it any less protective then dried bitumen when the hull scrapes against a rock?

The main issue (and it is true of most paints/coatings) is getting solvent out of the coating. All blacking paints will contain a significant percentage of solvent which is designed to evaporate once applied leaving pure bitumen which can then harden and provide a barrier coating. If applied at too low a temperature, of if put back in the water too soon that solvent will not have evaporated properly and will remain in the coating. In the event of putting in too soon, then it will be solvent trapped in the top coat. If overcoated to quickly then solvent can get trapped in the underneath coats.

Solvent is potentially bad as in the last 20 year the world has gone mad and we have been forced to use water soluble solvents (from HSE inputs) rather than the much better performing 'real' hydrocarbon solvents. If left in the coating, these water soluble solvents will attract water and allow it to get through the coating and hence potentially get to the steel and cause problems. Just a small % of solvent will also make the coating soft and so be far more likely to detach from the steel from impact damage.

I've never seen any tests done on blacking coatings so cant really comment if any of the above will have any significant effect on hull corrosion as blacking is such 'low tech' but it seems to work. I would always try and follow manufacturers recommendations on cure times/overcoat times/immersion times at the recommended temps to get the best possible performance - as there are plenty of other potential problems in coatings (surface prep, condensation etc etc) and therefore ticking as many boxes as possible gives you the best chance of success.

[jenevers]

11 hours ago, Dr Bob said:

The main issue (and it is true of most paints/coatings) is getting solvent out of the coating. All blacking paints will contain a significant percentage of solvent which is designed to evaporate once applied leaving pure bitumen which can then harden and provide a barrier coating. If applied at too low a temperature, of if put back in the water too soon that solvent will not have evaporated properly and will remain in the coating. In the event of putting in too soon, then it will be solvent trapped in the top coat. If overcoated to quickly then solvent can get trapped in the underneath coats.

Solvent is potentially bad as in the last 20 year the world has gone mad and we have been forced to use water soluble solvents (from HSE inputs) rather than the much better performing 'real' hydrocarbon solvents. If left in the coating, these water soluble solvents will attract water and allow it to get through the coating and hence potentially get to the steel and cause problems. Just a small % of solvent will also make the coating soft and so be far more likely to detach from the steel from impact damage.

I've never seen any tests done on blacking coatings so cant really comment if any of the above will have any significant effect on hull corrosion as blacking is such 'low tech' but it seems to work. I would always try and follow manufacturers recommendations on cure times/overcoat times/immersion times at the recommended temps to get the best possible performance - as there are plenty of other potential problems in coatings (surface prep, condensation etc etc) and therefore ticking as many boxes as possible gives you the best chance of success.

Interesting. In a way I can see a coating that doesn’t fully dry out, being more resistant to scratching, than the brittle tar I’ve seen on some boat hulls, that sort of shatters, (for want of a better word) when chipped at with a scraper. May be it’s  just old fashioned tar that does that.