What's the best method for blacking

[Bobbybass]

That doesn't sound like Comastic to me, certainly very different from my experience in which it's impervious to pretty much everything once it's hardened. I could easily believe bitumen would be affected by diesel etc though.

Genuine Comastic...as applied in 3 coats with my own fair hands...

Allowed a week to dry before back in the water...

[Chertsey]

Genuine Comastic...as applied in 3 coats with my own fair hands...

Allowed a week to dry before back in the water...

Onto shotblasted bare steel?

[Bobbybass]

Onto shotblasted bare steel?

 

I pressure wash...scrape a bit of rust...and then lay it on...

There is no way I would remove well adhered blacking...expose bare metal ..and then start again...you're just asking for problems..

Uncover metal...it instantly starts to gather moisture.

I don't understand why people should think that is a good idea...and waste their money ?

 

Last hull survey..after 14 years...showed little loss of metal ..so it must work.

[ditchcrawler]

I pressure wash...scrape a bit of rust...and then lay it on...

There is no way I would remove well adhered blacking...expose bare metal ..and then start again...you're just asking for problems..

Uncover metal...it instantly starts to gather moisture.

I don't understand why people should think that is a good idea...and waste their money ?

 

Last hull survey..after 14 years...showed little loss of metal ..so it must work.

But you said it was coming off under the sink outlet.

[Chertsey]

I pressure wash...scrape a bit of rust...and then lay it on...

There is no way I would remove well adhered blacking...expose bare metal ..and then start again...you're just asking for problems..

Uncover metal...it instantly starts to gather moisture.

I don't understand why people should think that is a good idea...and waste their money ?

 

Last hull survey..after 14 years...showed little loss of metal ..so it must work.

It doesn't sound like a waste of money if we have both used the same product and mine has stayed on while yours hasn't.

[STUBAG]

I did get rust along the waterline...until I changed marinas.

Somebody pointed out to me...that this could have been to do with oil and diesel spills...which strips comastic.

Thinking about it...they may have been right...as there was always a 'film' floating about...due to people 'bilge pumping' and self dieseling..

This is precisely why we no longer use yer average "blacking",but now STICK with Chlorinated Rubber brushing gloss.Lasts well, looks good,price is sinilar to Intertuf.

[bizzard]

I'd only scrape off the loose rust only and then whack the blacking on. By doing it like that over the years a good thickness of bitumen paint will gradually build up on most of the hull anyway making it possible to stretch out your docking periods. I'm up to 5 years now after 13 years, my last docking was 2007 and am docking again in a week or so's time.

[Bobbybass]

I'd only scrape off the loose rust only and then whack the blacking on. By doing it like that over the years a good thickness of bitumen paint will gradually build up on most of the hull anyway making it possible to stretch out your docking periods. I'm up to 5 years now after 13 years, my last docking was 2007 and am docking again in a week or so's time.

That's my point exactly. I do get some 'fading' along the kitchen/outlet side..and at one time..had a little line of rust setting up where other peoples bilge pumps were putting a film of oil etc on the canal... .but no point in scraping or shot blasting a surface that has nicely adhered protection.

I too..have a nice thick surface coat in most places that has built up over years.

Edited July 25, 2012 by Bobbybass

[Miracle]

i am none the wiser from having read this thread.

I've got a two pack hull that was stripped to bare metal and 5 coats applied.

do i have to go to bare metal each time I want to reapply the two pack or not?

[Canalwatcher]

I am booked in to do Zodiak's blacking in a couple of weeks time. Have done it twice previously using Rylards premium/rytex.

 

Trouble is when the boat was built (in 2007) cream two pack epoxy was applied to the bare steel and then intertuf on top and the blacking doesnt adhere well - last time we did a thorough preparation job but some of the blacking still came off as can be seen from the photo. We put on three coats of Premium at 24 hour intervals and left 3days before putting back.

 

 

The epoxy is still protecting the steel in the main so I'm not worried about corrosion it's more cosmetic. I don't want to go back bare steel this time (maybe in two years time?)

 

So is there something I could use to black that will adhere better than the Rylards to both the exposed cream two pack and to the previous Rylards blacking?

 

Mick

Edited July 31, 2012 by zodiak

[Badger]

My only comment would be..I wouldn't use Vactan where I will 'black'.

I have found that the blacking (Comastic in my case) is designed to grip onto prepared metal...and putting it over a 'skinning' compound like Vactan..it tends to pull off easily.

I found the same with red oxide...it didn't grip so well on that either..

 

 

I agree, last time I blacked my hull I applied underwater primer in a 12" band around the waterline area. Within a few months this primed area was back to the primer, the bitumen had all come off.

[swift1894]

My only comment would be..I wouldn't use Vactan where I will 'black'.

I have found that the blacking (Comastic in my case) is designed to grip onto prepared metal...and putting it over a 'skinning' compound like Vactan..it tends to pull off easily.

I found the same with red oxide...it didn't grip so well on that either..

 

Strange. When I bitumened the new steel plating repairs on my old boat, the instructions on the bitumen tin said "treat NEW steel with red oxide BEFORE applying the bitumen". Glad I read the instructions first rather than afterwards, like many people do

When I dry docked some years later some areas of bitumen had gone but ALL the red oxide was still intact and the metal underneath (just in a few small areas, which I scraped off just to see what was happening) was still as new.

It made me wonder why we don't just apply red oxide and forget bitumen etc

[Miracle]

still none the wiser. I've sanded the bits that rusted (3 small spots above the waterline) and overpainted with hammerite. 72hrs now and its not blistered so hopefully thats ok.

[Zayna]

Confused.com here again.

 

It's almost blacking time, and I've just read through all this and am, as usual, bamboozled.

 

When we had our survey done, the surveyor recommended stripping back to bare metal, applying a primer called Primercom then two coats of Intertuf blacking.

 

Is this no good?

 

Also, do you do each stage all at once or can you do it in sections - say a quarter of the boat at a time, so the bare metal isn't exposed for two long?

 

 

We are not paying someone to do this, we (the royal we, that means him) want to do it ourselves.

 

Thanks in advance. Again.

 

Z