Hull painting with Roller and Tipping

[Pauls]

Rustic, I'm concerned about the quick rusting after blasting you are seeing. The rust is proof that the blasted steel has contamination - typically referred to as "salts" on the surface.

Truly clean steel does not rust when exposed to air. It needs something to act as a catalyst to promote the oxidation we see as rust. I have blasted steel to a white finish and have had it stay perfectly the same, with no visible rust, months after the initial blasting. This particular example was the insides of diesel tanks, the access hatches were sealed so no water could intrude. They were dry, they had not been filled with diesel yet. I have blasted many steel panels and had them show no visible rust after several days of indoor storage.

Paint manufacturers typically specify a surface test after blasting for salts, sometimes referred to as ionics. Test kits are sold for doing this testing.

There is a company which sells a liquid for removing soluble salts from steel prior to painting. I have used it, it appears to work well, witness the examples above. Don't recall the name, a net search will pull it up.

I see the quick rust after blasting as proof that you have a salt contamination problem. It is possible that the salt is in the blasting media. You can test this by changing to a different media, blasting a test area, and observing results. I believe that the soluble salts remover, if applied immediately after your blasting, may also solve your problem. I strongly suggest that you test the surface for salts before you paint. Applying paint over a salt contaminated surface guarantees that the paint will fail earlier than it should.

Good luck on your project.

[Terra Nova]

You could apply Ospho to an area immediately following sand blasting. Don't wait for the entire hull to be blasted.
Ospho Rust Treatment - Since 1947

[Pauls]

Ospho, or phosphoric acid, which is a main ingredient in Ospho, creates a phosphate layer on the steel which is rust resistant. Phosphoric acid dipping is a very common paint prep step for some steel work. But this will not remove surface salts. You really are better off either eliminating the source of the salt contam or using a salt solvent to remove it.

[Terra Nova]

The contamination could be in the blasting media.

[Pelagic]

RC.. Since your original plan to prime immediately after a section was blasted, did not happen, ......I urge you to get a paint representative to inspect steel before using their product.

Reason I suggest this ...... is because you may need to switch to a primer more suitable for "machine Preparation", which has additives more forgiving to contaminates.

You may end up using a hand grinder with a wire cup to remove the contaminated rust even after using ospho.

Get their assessment and solution in writing, if you can.

Good luck with this.

[Rustic Charm]

Originally Posted by Pelagic

RC.. Since your original plan to prime immediately after a section was blasted, did not happen, ......I urge you to get a paint representative to inspect steel before using their product.

Reason I suggest this ...... is because you may need to switch to a primer more suitable for "machine Preparation", which has additives more forgiving to contaminates.

You may end up using a hand grinder with a wire cup to remove the contaminated rust even after using ospho.

Get their assessment and solution in writing, if you can.

Good luck with this.

g

Thanks Pelagic, I called the paint manafacturer the moment I realized I wouldn't be able to paint it immediately after sand blasting. It was his idea to use the acid to clean it of rust, then I need to use acetone or Norglass cleaner to remove the spent salts from the acid.

[Rustic Charm]

Originally Posted by Pauls

Rustic, I'm concerned about the quick rusting after blasting you are seeing. The rust is proof that the blasted steel has contamination - typically referred to as "salts" on the surface.

Truly clean steel does not rust when exposed to air. It needs something to act as a catalyst to promote the oxidation we see as rust. I have blasted steel to a white finish and have had it stay perfectly the same, with no visible rust, months after the initial blasting. This particular example was the insides of diesel tanks, the access hatches were sealed so no water could intrude. They were dry, they had not been filled with diesel yet. I have blasted many steel panels and had them show no visible rust after several days of indoor storage.

Paint manufacturers typically specify a surface test after blasting for salts, sometimes referred to as ionics. Test kits are sold for doing this testing.

There is a company which sells a liquid for removing soluble salts from steel prior to painting. I have used it, it appears to work well, witness the examples above. Don't recall the name, a net search will pull it up.

I see the quick rust after blasting as proof that you have a salt contamination problem. It is possible that the salt is in the blasting media. You can test this by changing to a different media, blasting a test area, and observing results. I believe that the soluble salts remover, if applied immediately after your blasting, may also solve your problem. I strongly suggest that you test the surface for salts before you paint. Applying paint over a salt contaminated surface guarantees that the paint will fail earlier than it should.

Good luck on your project.

Do you sand blast dry or wet?
And where are you situated?

[Rustic Charm]

Well, another day.

Today I finished off the grinding being very conscious not to upset anyone. Then I cleaned the diesel tank again, degreased it and sucked it all out with a wet Vac. Then it was finally time to put on the acid using a roller.. Initially it turned a light grey.

[Rustic Charm]

Two hours later and it was turning black as it's supposed to.

[ausnp84]

Looking good mate!

Just keep on truckin' with it - in another few days all your clothes, hair, dog, etc will be covered with paint and general stickiness, but hang there and it'll look great when it's all done

What are you using as paint for your diesel tanks?

n

[Rustic Charm]

Originally Posted by ausnp84

Looking good mate!

Just keep on truckin' with it - in another few days all your clothes, hair, dog, etc will be covered with paint and general stickiness, but hang there and it'll look great when it's all done

What are you using as paint for your diesel tanks?

n

cheers.

I'm using 'diesel' to coat the inside 😳

The problem is I can't access any of the diesel tank. I can only just get my arm in one half of the top because at the widest it's only 200mm wide and then slims down to just 25mm at the stern. After I have degreased and Vac the gunk out today I realized that someone has previously spilled something into the bottom of the tank.

[ausnp84]

Originally Posted by Rustic Charm

cheers.

I'm using 'diesel' to coat the inside 😳

The problem is I can't access any of the diesel tank. I can only just get my arm in one half of the top because at the widest it's only 200mm wide and then slims down to just 25mm at the stern. After I have degreased and Vac the gunk out today I realized that someone has previously spilled something into the bottom of the tank.

What does the spill look like? It's not a bad case of diesel bug, is it? Something we didn't do - that I still need to do - is install a small hand pump with a tube to the bottom of the diesel tank. A quick pump once a month goes wonders to keeping water out.

Diesel's a good tank sealer; we ran some of it through mild steel box section we couldn't paint internally and it's never rusted or caused problems.

n

[Rustic Charm]

Originally Posted by ausnp84

What does the spill look like? It's not a bad case of diesel bug, is it? Something we didn't do - that I still need to do - is install a small hand pump with a tube to the bottom of the diesel tank. A quick pump once a month goes wonders to keeping water out.

Diesel's a good tank sealer; we ran some of it through mild steel box section we couldn't paint internally and it's never rusted or caused problems.

n

It's solid and certainly looks like it's been poured in. Pretty much like some sort of resin. I'm moving my tank outlet tube to the deepest point so that it continually sucks up and filters contaminates and water.

[Wotname]

Originally Posted by Rustic Charm

It's solid and certainly looks like it's been poured in. Pretty much like some sort of resin. I'm moving my tank outlet tube to the deepest point so that it continually sucks up and filters contaminates and water.

Presumably this isn't your main engine pickup point, that wants to be at least an inch or more (say 2") above the lowest point IMO.
Then you want a drain at the very bottom to remove water and crud etc. The drain can be another tube with a small pump or can be a bung in the hull that you can drain when you slip.

If you ever plan to fuel polish, you could use this drain pickup.

[ramblinrod]

Originally Posted by Rustic Charm

Yeah that's right. The guy who's been complaining the most has a glass sail boat, but I'm not sure what his problem is as he went ahead and anti fouled today. Possibly just sick of the noise. But, the guy who complained the loudest directly to me, with about 15 minutes ago was angry because he reasons there are iron filings all over his very old decrepive fero motor cruiser. Which is not true. They are not iron, it's some sort of black sand. And I offered to wash his boat for him but then he said that's not the point. So, stuff him.

Ummmm, I believe when working in a boat in a yard, it is the doers responsibility to ensure that their actions do not cause negative environmental or personal property impact.

If a person plans to sandblast their boat (or do any other work that will cause airborne contaminants), they either need to skirt their boat completely to keep contaminants in, or cover nearby boats to keep contaminants out.

I subcontract to sand blasting companies and they know full well the issue. Any sandblaster who claims it is my responsibility to clean up after, I won't hire. Then there is no incentive on their part to exercise non-destructive environmental and property protection procedures.

And boy, have I seen what happens when these guys are let loose to blast away. 20 boats in a yard contaminated to clean the bottom of one.

Controlling air-borne contaminants when sandblasting a boat is equally important as a powerboater controlling their wake. If either damages someone else's property, that owner has every right to complain and expect proper redress.

Regarding offering to wash his boat, that was a responsible and courteous offer, but there are a number of things at play here:

1. I believe he is correct in saying that is not the point, the point is, the contaminants should be controlled at the source, so that he is not negatively impacted in the first place.

2. Nobody but nobody touches my boat, unless I am very sure they are more qualified than I (and there are very few). A well meaning person, could easily do further damage, mopping sandblasting grit into the gelcoat or paint finish.

3. Whether the other boat is POS or Mega Yacht to the doer, makes no difference to the owner, it may be everything they have, and represent their entire life's work and dream.

4. I know first hand how upsetting this can be. I've had to remove sandblasting grit from the exterior of my entire boat, and then service all winches to ensure the grit did not get into them. It took two full days. Had it not been a dear friend, they would have received a bill. Those two full days I could have been working on someone else's boat making full hourly rate. It likely have cost them twice what they paid for the sandblasting job (in their case, 1 days work).

5. Many yards have policies in place, defining the procedures that must be employed to prevent this type of problem.

6. When situations like this occur, it makes it harder for others in the future, regardless how good they are about minding other people's property.

As a professional yacht service provider, I have to be extremely careful about this kind of stuff. Repairing ten other boats after working on one, is not profitable. There is no obligation on any owner to let me perform the redress, they can call in who ever they want and invoice me. If I couldn't afford it, it would be an insurance claim, that could put my premiums so high, it would put me out of business.

RamblinRod
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