Cold Galvanising

[bristol & argo]

The self righting force of a 70' narrowboat is really quite large!

 

Richard

 

Ahh, what you need is a shopping trolly or old oil barrel, just lob it in the canal and drive the boat up it on one side...

 

 

 

Simon

[DHutch]

Hi Mike, interesting what you say about epoxy, I am beginning to feel quite ignorant about coatings, hence this post i suppose.

- So what primer under the bitumen? I assume you mean bitumen and not black tar varnish.

Our boat was painted with twopack epoxy blacking when she was new.

- Gritblasted inside and out, blastprimer on within half an hour, epoxyzinc over than the next day, then epoxy on the underside, and twopack polyurethane on the topsides and inside.

 

Leigh's then discontinued there epoxy blacking, and we switch to there underwater vinyl, which we find to be as good, and easier to apply.

- We also paint the underside of the baseplate. And diespight being a little over standard draught (2ft8ish) and moving her about a fair bit, there was very little bare steel when we docked this easter after four years in the water.

 

Ive said this about a dozen times before, and probably sound like JohnO on a rant, but quite honestly i think the stuffs great, as do most other people who see us in drydock.

 

 

 

Daniel

[Chris Pink]

Our boat was painted with twopack epoxy blacking when she was new.

- Gritblasted inside and out, blastprimer on within half an hour, epoxyzinc over than the next day, then epoxy on the underside, and twopack polyurethane on the topsides and inside.

 

Leigh's then discontinued there epoxy blacking, and we switch to there underwater vinyl, which we find to be as good, and easier to apply.

- We also paint the underside of the baseplate. And diespight being a little over standard draught (2ft8ish) and moving her about a fair bit, there was very little bare steel when we docked this easter after four years in the water.

 

Ive said this about a dozen times before, and probably sound like JohnO on a rant, but quite honestly i think the stuffs great, as do most other people who see us in drydock.

Daniel

 

Hi Daniel

 

it does seem that epoxy is the one, the other advice is to bitumen over the millscale and then keep re-doing it every 2 years until the scale is off but the economic of that with the current prices for docking make the eyes water. Probably best to bite the bullet.

 

Did you do the job yourself? how was the underside grit blasted?

 

 

Our local epoxy specialist is very reluctant to do the bottom, i can sort of see his point that not much oxidation happens under there but the 1st boat I had was painted underneath and the surveyor was well impressed and i think the yard (inside on a trolley) means that jacking the boat up is a bit of a faff. Doesn't come in much cheaper than flame spraying there so if it is possible to do the job ourselves there's a lot of money for tooling in that kind of budget.

 

Thanks for your help (and everyone else on this topic) the mists are clearing....slightly and slowly.

 

edited to add;

 

i am going for red lead on the inside, i have found a supplier who claims to go to the maximum the BS allows on the quantity of lead oxide £60+VAT for 5 litres not cheap but i do like the stuff (must have eaten some as a baby).

Edited November 28, 2007 by Chris Pink

[DHutch]

The grit blasting was done for us, well my grandad as it was all a bit before my time.

- Im not sure about the gritblasting of the bottom, but i shall ask him next time i see him if your interested.

- For drydocking we always use/have used worsley drydock, which has excellent underboat access for painting etc.

 

 

 

Daniel

[smileypete]

I have been looking into zinc flame spraying and it is expensive - around £3k for my 50' hull but reckoning on 20 year life could still be my coating of choice.

 

Is that the whole hull or just the bottom half?

 

i am going for red lead on the inside, i have found a supplier who claims to go to the maximum the BS allows on the quantity of lead oxide £60+VAT for 5 litres not cheap but i do like the stuff (must have eaten some as a baby).

 

Personally I'd run a mile from any boat where the inside is done with red lead.

 

I'd look at zinc rich primer for anywhere below the waterline vulnerable to damage, and zinc phosphate primer elsewhere.

 

cheers,

Pete.

Edited November 28, 2007 by smileypete

[Chris Pink]

Hi Pete

 

Is that the whole hull or just the bottom half?

 

There is only a bottom half at the moment, kind of based of his broad estimate of £50 per sq foot, but there are still a few variables - he doen't like to do the blasting for instance but the £50 included blasting so is probably a bit more expensive than needs be. I have also been pricing up doing my own blasting, Brandon hire the kit.

 

Personally I'd run a mile from any boat where the inside is done with red lead.

 

Tell me more

I'd look at zinc rich primer for anywhere below the waterline vulnerable to damage, and zinc phosphate primer elsewhere.

 

Why not zinc phosphate below the waterline, i would be grateful for a bit more information here.

[smileypete]

Is that the whole hull or just the bottom half?

There is only a bottom half at the moment, kind of based of his broad estimate of £50 per sq foot, but there are still a few variables - he doen't like to do the blasting for instance but the £50 included blasting so is probably a bit more expensive than needs be. I have also been pricing up doing my own blasting, Brandon hire the kit.

Is that £50 per linear foot? Not outrageously expensive. Might even be worth getting the shell delivered to a facility that can do it, then onward for completion.

 

I'd also consider getting the front and rear bilges done, boats often rust from the inside and bilges get used for storage and bashed around.

 

Personally I'd run a mile from any boat where the inside is done with red lead.

Tell me more

Just seems a bit of a liability using it for a habitable space, for not much extra benefit.

 

I'd look at zinc rich primer for anywhere below the waterline vulnerable to damage, and zinc phosphate primer elsewhere.

 

Why not zinc phosphate below the waterline, i would be grateful for a bit more information here.

I could have phrased that better, basically zinc rich primer for anywhere that might get damaged eg bottom of bilges, and zinc phosphate elsewhere.

 

Something worth considering is some topcoat paint won't stay on zinc or zinc rich primer, so a coat of primer is needed between topcoat and zinc.

 

Basically do lots and lots of googling, there's at least one metal boat forum (metal boat society?) that could be a good source of info.

 

cheers,

Pete.

[Chris Pink]

Is that £50 per linear foot? Not outrageously expensive. Might even be worth getting the shell delivered to a facility that can do it, then onward for completion.

 

 

No it was me being careless, it is £50 per square metre ie £3,000 based on 60 square metres. Not economic to move the boat to do it, easier to move the people to the boat.

 

Red lead is not really a health issue in these conditions, white and grey lead are the more toxic forms and as such are banned under EU rules. As none will be exposed in the finished boat I feel it is safe to use this as a substrate. There won't be much hull visible.

 

Still not sure what you mean by the difference between the use zinc phosphate and ordinary zinc primer (does ordinary zinc mean the cheapo stuff that eg Liverpool boats are delivered in?). Could you explain a bit more about this.

 

I am googling and talking and learning, but you'll appreciate there's many different opinions so the more discussion the merrier. There's also the issue of budget and budget over time and long term resale values. not simple

 

Thank you for your help

[Timleech]

Red lead is not really a health issue in these conditions, white and grey lead are the more toxic forms and as such are banned under EU rules. As none will be exposed in the finished boat I feel it is safe to use this as a substrate. There won't be much hull visible.

 

Red lead is a real health issue for the poor s*d who gets the job of repairing the boat at some future date, or even cutting it up for scrap, especially so if he doesn't expect to find it there because the boat is 'too recent' for it to have been used.

 

Tim

[smileypete]

Red lead is not really a health issue in these conditions, white and grey lead are the more toxic forms and as such are banned under EU rules. As none will be exposed in the finished boat I feel it is safe to use this as a substrate. There won't be much hull visible.

I still wouldn't do it, especially without expert consultation.

 

Still not sure what you mean by the difference between the use zinc phosphate and ordinary zinc primer (does ordinary zinc mean the cheapo stuff that eg Liverpool boats are delivered in?). Could you explain a bit more about this.

 

This web page goes some way to explaining it:

 

http://www.paintcenter.org/rj/feb04q.cfm

 

There's also zinc silicate paint, worth a look at.

 

I've no idea what primer LB use, probably a plain grey primer.

 

If I had a new build hull and price was not a problem, grit blast and zinc spray would seem ideal. I have considerable experience of the process in the aircraft industry. If properly applied it's firmly adherent and the slightly rough and porous film would be a good base for paint. Unfortunately, I have no idea of where you could get it done or how much it would cost.

What would be your second choice after zinc spray at all?

 

cheers,

Pete.

[Chris Pink]

What would be your second choice after zinc spray at all?

 

Probably the epoxy. The jury is still out on doing the bottom, i'd like to.

 

It does seem there's no hurry, best advice says don't do anything that i want to last until the humidity drops - April/May next year.

[RichardN]

Does anyone have any information about cold galvanising processes?

 

The paint, suppliers, applicators, including the blasting (in the South West) etc.

 

I had a 1970s narrow boat whose hull had been cold galvanised and even after 25 years in the water there was absolutely no corrosion damage whatsoever - brilliant.

 

Out self build shell will be ready for launching in about a month and this is my coating of choice for all surfaces around and below the waterline.

 

Chris

 

 

Cold galvanising to me means using a paint which has 90% + zinc content. This means using paints such as metaflux, zingard or zinga - http://www.zinga.co.uk/zinga_main.html . These paints are expensive but give you fantastic protection thanks to the sacrifical action of the paint.

 

Someone has mentioned Leighs paints - not cold galvanising but their two part epoxy micaceous iron oxide paints will give you excellent durability - could be worth talking to them http://www.wjleigh.co.uk/ to see who and what they recommend. I assume that you are thinking of getting the boat dropped off somewhere and painted before launching? Could be awkward at this time of year. Hopefully manufacturers such as Leighs may have lists of painters who may be able to help.

 

With all these systems you need to shot blast first and apply paint within 4 hours. Whether you use red lead (move with the times folks), dulux or something posh I think it is always worth shot blasting. Corus (British Steel as was) publish some good guides to this - see http://www.corusconstruction.com/en/refere...work/corrosion/

[The blacksmith]

Does anyone have any information about cold galvanising processes?

 

The paint, suppliers, applicators, including the blasting (in the South West) etc.

 

I had a 1970s narrow boat whose hull had been cold galvanised and even after 25 years in the water there was absolutely no corrosion damage whatsoever - brilliant.

 

Out self build shell will be ready for launching in about a month and this is my coating of choice for all surfaces around and below the waterline.

 

Chris

Hi Chris.

 

I have had extensive dealings with cold galvanising on steel hulls over the past 20 years. It is quite simple to tell if a boat hull is either galvanised or painted. Get an electrician (or a friendly inspector) with a potentiometer and ask him to measure the potential between the zinc coating and the hull. If the hull is galvanised you will get a reading of around 1.04 volts. When the hull is in the water the reading will drop to 0.85 volts. This is called the 'closed circuit' voltage.

 

If the coating is a zinc paint, then you may not even obtain a reading at all!

 

I know for a fact that over 80 narrowboats have been cold galvanised in the UK the past four years, and several have scraped their strakes (and hulls) on concrete lock walls and jetties etc and guess what? Not a bit of rust anywhere.

In my dim and distant past (I was a chemist in a former life) I used to advise boat owners on topcoats. Bitumens were widely used for many years, but they used to lose some of their consituents (plasticisires etc) through leaching into the water and they became brittle and would crack and come away under impact. The new hull blacking coming out in May is a fantastic replacement for this. You just slap it on over the cold galv with a brush and that is it!

Speak to Uniprep in Poole for ideas on blasting and coating on boats. They have been around for a few years and seem quite competent.

By the way, red lead primers were banned decades ago and are not legally allowed to be used anywhere near water due to the toxicity.

[Big Steve]

Galvafroid is the mutts nuts when it come to cold galvanising paint.

[Jane-Heidi]

Hello fellow boaters, we are a small family run business in Seaford who make cold galvanising compound called Rust-Anode. I have attached a file to explain why Rust-Anode is better for metal than just an ordinary primer. It should protect your metal from rust for upto 20 odd years. The best thing is that we make it in the UK and sell direct to end users - so it is A LOT cheaper than our competitors. My friend who also owns a narrowboat applied it to the whole of her boat and loved how easy it was to apply. It is a battleship grey colour and can be painted over with any top coat. No need to go to a chandlery and pay over the odds - you can buy direct form our website and we deliver the next day. I know life on the cut is hard, especially at this time of year so we are also offering a discount for anyone with a boat. Just contact us direct from our website. We can also answer any questions you may have and are open to any new ideas you may have for products that you may need but cannot get hold off - we have a resident boffin as the MD. Have a look at our website and give us a try: www.candpdevelopment.com

[Jane-Heidi]

Rust-Anode is a cold galvanising compound (paint or spray application) and it self sacrifices - which means if you scratch the metal - the Rust-Anode will self sacrifice and protect even the scratched part of the metal. The problem is that there are many companies out there selling Primers etc with Zinc but none have the amount of zinc or the highest spec of zinc to really protect for 20odd years. You need to carefully read the spec sheets. Also, these companies sell to third parties distributors who also want to make their cut so it can end up being quite a costly experience. We at C&P have been making Rust-Anode cold galvanising in the UK since 1952 and decided to sell the end user instead of distributors. Although this means we do not make as much profit - we are only a small family run business and are just happy to provide a good old fashioned service with a reasonable price for our products. You can have a look at our website for further reading, buy direct from us (24 hour delivery) and we are happy to answer all your questions - in fact we can answer your questions as we make the stuff and you wont be put on hold to some telephone place in another country - we are in Seaford. www.candpdevelopment.com

[Tony Brooks]

First post reported as commercial spam - although useful.

 

Jane-Heidi - have you asked the mods for permission to advertise.

[Chris G]

"shock tested between -4OOºC ..." - interesting temperature: -273C is absolute zero.

[Jane-Heidi]

HI Tony, thanks for pointing out that i need to ask Mods - no idea how to do this. Just wanted to give all boaters a bit of a boost in this weather with a discount. Don,t know how else to reach you all.

Jane

[tree monkey]

21 minutes ago, Jane-Heidi said:

HI Tony, thanks for pointing out that i need to ask Mods - no idea how to do this. Just wanted to give all boaters a bit of a boost in this weather with a discount. Don,t know how else to reach you all.

Jane

Tony has "reported" the thread, this will highlight the thread to the mods and I am sure they will review the issue.

 

Adverts that are useful to boat owners are tolerated, particularly if you involve yourself in the forum and don't spam the place with adds.

 

Welcome to the forum 

[Tony Brooks]

27 minutes ago, Jane-Heidi said:

HI Tony, thanks for pointing out that i need to ask Mods - no idea how to do this. Just wanted to give all boaters a bit of a boost in this weather with a discount. Don,t know how else to reach you all.

Jane

 

Unfortunately you posts coincide with another thread that now looks as if it might have been commercial advertising getting locked for future comment with no reason given.

 

If you click on Browse in the header and select staff you can send one of them a message or I think that you can post in the "for sale" section where it will be approved or not.

 

Personally I think your first post may be useful to members but if we are not very careful the forum will be flooded with commercial spam from all over the world.

 

 

Edited January 17, 2023 by Tony Brooks

[ditchcrawler]

Maybe the mods will post whether this is acceptable or not.

[john.k]

Arc spray zinc on a grit blasted white steel is the most effective ,and can be sprayed on thicker than hot dip (but usually isnt)...........new build .steel sailboat hulls are generally arc sprayed ,as rich people want the best.

[harrybsmith]

What surface prep is required for your product to work? Most cold galv solutions seem to require Sa 2.5 and if i'm honest I can't be bothered to blast all the new steelwork on my shell when something like an MIO primer just doesn't require that and has similar properties and I can just scabble/ cup brush it to bright steel (which will remove the mill scale as currently has surface rust) and crack on 

[Tony Brooks]

45 minutes ago, harrybsmith said:

What surface prep is required for your product to work? Most cold galv solutions seem to require Sa 2.5 and if i'm honest I can't be bothered to blast all the new steelwork on my shell

 

I would point out that maybe 30 to 40 years ago I had the thin steel ridge capping on my cement asbestos garage roof blasted, but the steel was so thin total rust removal was not possible. When I got the sections back, I painted them with the recommended number of coats of Galvafroid, no other coatings on top. So far it has kept the rust at bay. Based on that, I suspect the Sa 2.5 or what ever is more giving the manufacturer a get out of jail free card for when things go wrong than strict need.