advice needed on shot blasting interior of steel hull

[seasofcheese]

hello,
i am researching the preparation of interior steel for painting. it is more complicated than working on exterior because of confined space, dust and a lot more angled structures which are hard to reach. i concluded to three options: 1. needle gun which does not extract as much dust
2. shot blast with a small unit from hire shop
3. get contractors to do it
the first two options would probably take me a month to do and because of such a moist season i would get dubious paint results. the last option is the most attractive because it would take a few days to get the whole hull done to SA2.5 standard. it is very expensive as well- i have been quoted by one professional chap to get it done for £1500 which would take him three full days and another company quoted £2500 for this work without seeing the hull. it is 38x12' on hardstanding in Watford.
my questions would be:
has anyone shot blasted or needle gunned interior of their hull themselves?
what methods and ppe have you used?
can anyone suggest a pro shot blaster based not too far from Watford?
many thanks in advance

 

[prv]

Have to say, from everything I've read about shotblasting steel hulls, if paying for the job is remotely within your budget then it would be money well spent.

Pete

 

[Wansworth]

On my steel hull I apllied waxoyle and after ten years did not noyice any significant rust.A mate of mine had a small shot blassting set and shot blasted areas he need ed to paint like the engine space.

 

[Tranona]

No contest. Pay the man the £1500 - cheap. Steel hulls rust from the inside as that is where all the nasty little bits are that collect water unseen. If it is blasted properly and coated immediately you are ahead of the game.

 

[seasofcheese]

there is a good part of interior that has good epoxy on top but still i'm in favour of shot blasting all off even though i have no budget for it. will have to sacrifice. here are few pictures so you get an idea.

 

[nedmin]

Having had steel boats for over 30yrs I would pay the £1500 ,i,m sure if they make a good job you wont regret it.Then buy a few aerosols of Comma Waxoil and spray in joints were you can.Its a brilliant product,also excellent for spraying around window frames etc.It leeches into gaps and because its wax you can polish the excess off and it shines like wax polish!

 

[seasofcheese]

i doubt if wax can hold rust longer than epoxy primers if treated the same, what are your experiences on this issue?

 

[nedmin]

I didnt mean instead of epoxy but it will get in places that might be missed after .I find its useful such as when drilling a hole etc.I also spray every season round the ally window frames,, stainless parts that are bolted down.In fact anywhere that something is fastened down.

 

[Loch Linnhe]

Why don't you look in to hiring a shot blaster and compressor, I own one and the job you are looking at is fairly easy with the right kit, just make sure you use shot blasting grit not sand, £1500 is the grit and fuel on top of this?

 

[Deleted member 36384]

I have needle gunned extensively in the past. You will not get the surface finish that you need for good adhesion of the paint. I spent a few years re-needle gunning after failed paint jobs - I guess someone else is still re-needle gunning today because its cheap. It's a noisy, dirty job and can potentially cause 'white finger'/'dead man's hands'. Something to do with the vibration and blood flow being restricted.

I pay for shot blasting.

 

[daveyw]

Done it myself. Had a breathing hood. Major job. Getting in and around all the frames making sure you haven't missed any parts is time consuming. Then you have to remove all the blast material and then get the chosen treatment on sharpish to minimise the development of surface rust. I used rustbullet. Expensive stuff and didn't go as far as I was expecting, had to order more and it was very fumy. Needed extra ventilation to avoid aphyxiation! Great stuff and it sticks like s..t. Don't get it on your skin as it will only wear off, not clean off!

If you can get it done for £1500, do it!

 

[Robg71]

After working in ship yards and diving industry, the best surface for paint adhesion is definitly grit blast.
Its not a one man job if your doing it yourself. Need at least another pair of hands on the grit pot, and another pair for safety sake helping around.

Get an industrial hoover in to help with the clean up. Its a far superior finish to needle gun, and far quicker.

 

[PCUK]

The boat is a huge investment. The £1500 is a small portion of the cost but probably the most crucial part of the build. I know it can be hard when the cash isn't there but this is one expense you will always be glad you forked-out for.

 

[rogerthebodger]

Did mine 6 years age. Only way is grit blast and with your size of boat only way is to get some one in to do it

Pics of mine.

 

[Wino]

Why do navy still insist on grit blast? Its Noisy, dirty and dangerous, but they still do.

Have a look at the paint spec. for the coating you are going to use, for preparation it will say grit blast to SA2.5 To get that finish all over you need an experienced contractor.
Does his price include priming? It is essential that bare metal is coated as soon as poss. otherwise you will soon have a layer of 'gingered' metal.

 

[KellysEye]

There is a pen sized sand blaster for interior use. The first coat of paint should be zinc rich epoxy. Paint should be applied within 10 to 15 minutes of blasting, otherwise you risk flash rusting, so do sections at a time. Start at each end of the boat moving towards the cente to avoid contamination.

 

[ianj99]

There is a pen sized sand blaster for interior use. The first coat of paint should be zinc rich epoxy. Paint should be applied within 10 to 15 minutes of blasting, otherwise you risk flash rusting, so do sections at a time. Start at each end of the boat moving towards the cente to avoid contamination.

I suggest this companies products. I've used them for 2 years with excellent results, no adhesion problems but watch the fumes in an enclosed space as they contain much solvent.

http://www.rust.co.uk/epoxy-mastic.cfm

See their zinc rich epoxy:

http://www.rust.co.uk/popup.cfm?p_n=405029&p_i=405029

"EPOXY-ANODE zinc rich epoxy primer offers the very best in Cathodic and Barrier protection to BLAST CLEANED STEEL. To form part of a paint system with EPOXY-MASTIC.and other high performance coatings within our range.Epoxy-Anode is a self repairing primer containing 93% Zinc solids bound into an epoxy resin. If a scratch appears on the steel that goes through the topcoat and primer back to bare metal the zinc in the primer will react with the steel, this reaction will form zinc salts that will heal the scratch maintain the barrier and the steel will not rust.(Cathodic Protection) Epoxy anode comes complete with Base Hardener and 250 ml of thinners - epoxy anode is an isocyanate free primer Price: £29.95 "

 

[Elessar]

There is a pen sized sand blaster for interior use. The first coat of paint should be zinc rich epoxy. Paint should be applied within 10 to 15 minutes of blasting, otherwise you risk flash rusting, so do sections at a time. Start at each end of the boat moving towards the cente to avoid contamination.

you will have done about 15 sq cm in 15 mins with a pen blaster. And I doubt you'll get it to SA2.5.

Cheesy - £1500 is fair quote. It's absolutely horrible job blasting inside like that. Pay the man.

 

[Pasarell]

Elessar is right except that I would say it is a very good price.
Get yourself very well organised before the start. Ensure good extraction to remove airborne dust as much as possible - the blaster will work faster and you will be able to get in more quickly after he finishes. Ensure you have an efficient means of getting rid of the spent grit and debris quickly. There will be a lot of it.
Ensure the blaster knows exactly what you expect, especially in relation to the weld seams, ribs, stringers etc. If you are asking for Sa2.5 make sure you know what that means and be prepared to say it is unsatisfactory. When managing painting projects the most frequent thing I say to blasters is "Do it again". When they tell you it is OK for your paint scheme they are almost certainly wrong!

When the blaster has finished concentrate on getting the whole interior clean and dust free, especially around welds, angle brackets ribs etc.If you have a dehumidifier use it. If not, ensure good ventilation. The comments about getting paint on in 15 minutes are ridiculous and wildly impractical. Eventually the surface will ginger or flash rust but this will take hours in a dry environment and is not a particular problem nowadays.
Once clean the first thing to focus on is getting a stripe coat on all edges, corners, welds stringers ribs etc. A stripe coat is a brush applied primer to help build film on the areas most vulnerable to break down in the future. When you have that put on a good quality surface tolerant blast primer. Usually an epoxy applied quite thinly to hold the blast. Apply by spray if you can but that will need a whole new level of specialist application and safety equipment so brushing / rolling may be more practical. Enlist help if you can - it will be hard work. Once the holding primer is on stop and have a cold beer. You will have earned it!
Avoid rust converters like the plague. You've spent a lot of money and effort and rust converters will be actively harmful.
You can go with any of the fringe wonder products mentioned above or you can feed off the back of huge research and development by the major paint companies and their major clients. Big oil companies are incredibly careful about what they use and test every detail to death. Why anybody would ignore all their work amazes me. Products from International, Hempel, Jotun, Chugoku etc are excellent and well proven in these situations. Products from Dulux are not!
I certainly don't know everything but I am sitting in KL airport as I write this having just spent a few days working as a coatings consultant for a large offshore gas project as they prepare and coat subsea equipment.
Good luck and hope it all works out well

 

[seasofcheese]

thanks ever so much for your inputs, especially Pasarell (i know, KL airport is quite a boring place, but at least they provide free wifi)

just a quick update, i got two more quotes: symblast quoted £2500 after only seeing pics, radford priced £1500. i am keen to stick with the first man because £1500 is for three full days blasting to sa2.5. materials and fuel is included in price. he intends to use coarse sand because glass he says is not strong enough to take out scale. grit for the bottom part where corrosion is worst. doing it myself falls out as an option because we have a very wet season and i have not a very healthy lungs.

i have international intercure 200 ready and a spray gun. just a couple more questions- why paintbrush first coat on seams and welds? wouldn't diluted epoxy get in to crevices much better when being sprayed? would you recommend a topcoat(i have 40 litres of interfine 979) after 4 coats of primer for interior of the hull?