Sandblasting using a pressure washer & wet blast kit- anyone?

[Kev Williams]

I have 600 sq ft of steel houseboat hull I need to sandblast, dry blasting with a basic 100# pressure pot and 60 gallon compressor just ain't doing the job, and I'm not really into the roughly $1000 per hour rates for someone else to do it...

--I've been attacking this hull many different ways, none all that great-- angle grinders, wire brush wheels work great on rust and loose paint, and get into the rust pits ok to so-so, but they barely touch several layers of bottom paint, and they only work well for a few minutes... once the wires take on a bend, they do more skidding around than cutting. Sandpaper wheels cut thru the paint like gangbusters, but don't work well on rough rusty areas. And they clog up quick. Tried a wheel with carbide chips, it's great for cutting thru paint but I wore it out quick, and it wasn't cheap. Plain sandblasting is frustrating- it works great on the rust and pitted areas, but it's slow. And it's real slow to remove the paint. And even with a 60 and 30 gallon compressors tied together, it takes a couple of minutes to do a square foot, and then then I'm below 100psi and using air faster than the compressors will replace it. Have to wait on the compressors. And messy, my gawd!

So after searching out dust-free sandblasting services, I found out there's wet blasting attachments for pressure washers! Watched a few videos- not quite as efficient as the big wet units, but they do seem to work, provided you have enough pressure washer to draw the sand. Some looked ok-ish, the one by Power Eagle worked quite well on an old painted and rusty steel tank, it ran off a square foot a lot faster than my sandblaster will.

HD has some reviews on one they sell, mostly bad, but mostly because the user's pressure washer is inadequate. Mine is 2800 psi, and it's probably inadequate too, BUT- I'm not against buying or even renting one with enough grunt, and also, I DO have the luxury of already having a sand delivery system, which it seems to me would be no big deal to set a pressurized flow rate that would work...

So just wondering if anyone's used one, and if you like it?

[Wayne Lomman]

Kev, I have been blasting and painting for a fair bit of the last 20 years - between woodworking - and there are some basics. DONT USE SAND! Use some other abrasive so we don't hear about your demise from silicosis.

First, any blasting is messy. Dry you sweep it up, wet you hose it down. Your choice but it is messy. However, dry you blast until 2pm, dust it down and paint the clean area before it flash rusts. Wet, you watch it flash rust as you blast and you have to let it dry etc etc. You end up with a compromised job.

Dry blasting is the quickest and easiest unless you have access to a very high pressure water blaster in 20,000psi+. The units you are looking at will not help your problem.

Your main problem is air supply. You don't have enough. Hire a decent compressor for the job. 60 gallon is a measure of the tank. You need more cubic feet per minute - cfm. Check your blast pot to see what cfm it needs to run at 100psi and hire a compressor at least 25% bigger.

Your productivity of 2 minutes per square foot is a bit low. If my guys can do 100 square feet per hour I am happy. You are getting 30 square feet per hour. To fix this, first fix the compressor problem. That will help a lot. Next, blast at a 45 degree angle to the surface pushing against the paint and leaving bare steel behind. Do it once like you are colouring in at primary school. Remember when messy colouring in got your knuckles whacked? Welcome to blasting!

The paint on the surface makes a difference too. Is it shattering off or peeling back like plastic? Most likely the second option in which case you have to be patient. Too many boats use thermoplastic paints and they are always a mongrel to get off.

They guys wanting to charge you a grand per hour are on a good paddock. That's more than double what it should be worth, even allowing for higher Australian wages. Should be one days work for a half decent contractor. Plenty more advice if you need it. Cheers

[Jerome Stanek]

I have a 3500 psi pressure washer with a sand injector that works great on stuff like paint on concrete. I used it to remove gum off sidewalks for a drug store chain. But it will rust steel real quick.

[Dave Lehnert]

Just toss this in for sake of discussion. I have no experience using this kind of blaster. Only became aware of this type of blaster because a company, Coldjet, is local here.
Looks like Dry Ice solves the mess problem????


https://www.youtube.com/watch?v=l_9nITRz--0

[Kev Williams]

I know you shouldn't use sand to sandblast with due to health issues, but that leads me to a dumb question: Why do we buy the stuff for our kids to play in?

That said-- where the boat is, wet blasting will be preferable to dry, although a few HF tarps could contain the cloud from dry blasting. The other issue with dry blasting is the suit of armor needed. And I'd be happy to get 50 sq. ft an hour, that would make it only a weekend job!

I've been looking to buy ground glass, but I can't find a local supplier, at least online, and $30 a bag ($8 plus $22 shipping) (Northern Tool) is a bit steep...

My 2 compressors together move around 14 SCFM at 90 psi. I have a friend who may still have a his big diesel screw compressor, but having fallen on hard times I'm thinking he's sold it. Phone call is in order!

[Lon Crosby]

Do a better search on Google - say 40/70 Grit Ground Glass Media. Lots of manufacturers so depending on where you live, there should one or more local manufacturers (for local pick-up) since it is just ground bottle glass. You may want to specifically search for a mfg that grinds recycled plate glass as it is harder and may work better for your app.

[Wayne Lomman]

Yes, 14 cfm won't do it. Get something like your friends compressor and it will make a world of difference.

Sand is hazardous when broken down extremely fine. You can live on the beach and not get silicosis. Sandblasters used to routinely die in their 50's if they were lucky.

Dry ice is very specialised and very expensive. Best used where clean up is impossible. The down side is you don't get a surface profile for paint adhesion. Cheers

[John C Cox]

I think when you total up all the materials and supplies - you may find $500-$1,000/hr is not all that bad...
Especially when you consider the specialty media that cuts fast, tarps, masking, respirators, filters, bringing it all with them, setup/cleanup, and all the rest....

If those guys are doing 100+ sq-ft per hour - they are going through a LOT of media - thats probably a pallet or 3 of media in your 600sq-ft boat hull... And thats all part of your cost...

[Jerome Stanek]

Have you thought about a scaler

https://www.amazon.com/Nitto-Kohki-EJC-32A-Electric-Needle/dp/B00NV7IV8W/ref=sr_1_1?s=industrial&ie=UTF8&qid=1493650204&sr=1-1&keywords=electric+needle+scaler

[Ruperto Mendiones]

Could you rent a big diesel compressor and/or a complete sandblast outfit?

[Kev Williams]

thanks for the advice everyone-- :)

needle scalers, never heard of them. Looks like they would do a good job really, was trying to locate a video of one being used on something bigger than an old drill press base to see how fast they work. I have to wonder how well the $985 version Jerome linked to works vs. the $80 types.

According to a certain website that sells sandblasting equipment, they're using six $10 bags of ground glass media per hour of blasting. That's plenty reasonable as far as media goes, IF i can find it for that price...

To give you an idea of the task at hand-- this is just about half the bottom, maybe a snick more...

359484

Stray current corrosion caused it...

[Wayne Lomman]

Kev, abrasive blasting is your only option to get anything like a job that you won't have to do over again in a couple of years. It gets you a white metal surface which is essential for full submersion and it gives you the surface roughness you need for paint adhesion. Your power tool options are not going to do the job. Talk to your paint supplier about a correct coating system and procedures as you need to monitor relative humidity, temperatures of air and steel and calculate dew points. Don't cut corners. It just shortens coating life. Cheers

[Marilyn Johnson]

Considering the challenges faced with conventional methods like dry blasting and sanding, exploring wet blasting attachments for pressure washers seems promising. Given your existing equipment and willingness to invest in a more powerful pressure washer, it could potentially offer a viable solution for your steel houseboat hull. Although reviews vary, your preparedness to adapt the sand delivery system might enhance its efficiency. Exploring user experiences with similar setups can provide valuable insights before making a decision.

[Warren Lake]

Not up on the new ways but have seen some you tubes of stuff that looks good. Im old school in a cabinet starting over 40 years ago home made and Silica. Some friends who are set up went from silica to glass. One blasts at 200 PSI with three compressors and an auto spray booth with a crane., At that level it goes fast and works great.

I only had one compressor 80 gallon 2 stage and 5 HP I needed two same but did it on one. You need understand that the different grits make all the difference in the world. I went to Aluminum Oxide and it rips rust off, silica was little tiny tennis balls and useless compared. I can blast at 25 PSI even and it works cause the grit is so sharp. It breaks and gets smaller, im in a cabinet with a woodworking dust collector and blast gates. I probably normally did car parts and 45 to 65 PSI. Depends on the parts as well. Now this is contained so im re using the same stuff over and over then after time add another bag in. I use 56 grit as it leaves a fine surface. Ive done glass bead past and it leaves a nice surface but it breaks on impact. The AO breaks and gets smaller but it still has sharp edges so it continues to cut. This is the same principle as sandpaper. When you run through the wide belt its breaking off and exposing new sharp surfaces.

My friend at high pressure has a crane to rotate parts and wears a suit as well and has a larger hose and nozzle. Lots depends on being set up. Lots of mickey mouse equipment in woodworking and you can get by some amount. Forget that with sandblasting as its going to be a painful experience. My friend has never waited for air with three large compressors very high pressure and all compressors in a sound proof room so you never hear them. This is one thing you need to be set up for.

If was doing car frames id be degreasing then blasting in a room to reclaim the sand. If you dont degrease then you will have crap in the sand. Okay if the crap is rust that you have blasted off already never an issue with that. Car parts done right then not handled by hand but a glove or cloth then epoxy primered or Vynil was and top coated right stiuff will last really well. Parts done my old truck are still the same as when done or very close. They were painted old RM epoxy primer and Imron on top. You need to be set up to use that and sure there are other materials now im not familiar with.

[Tom M King]

I like the pressure washer blaster because it's not dusty. You need to use pool filter sand. Being careful not to hit any part where it comes right back at you and it's not too bad. I bought a cheap kit off Amazon to work on some tractor parts not really expecting much, but it did what I needed to do just fine. I watched a couple of youtube videos, and both suggested the pool filter sand, so I didn't do any experimenting any differently.

The one thing I don't like about it is the part that needs to be primed immediately is soaking wet. I dry it with a torch and prime while it still has some heat in it but nothing steaming off any more. Stuff I did 6 or 7 years ago is still holding paint great.

This is not a job for someone who is unco-ordinated and not used to working with tools.

My largest pressure washer is 2500 psi at 4.4 gpm. The blaster would work better with a higher pressure washer, but I have this one for working on old houses and don't need a 3500 psi one enough to buy one. It works pretty good with the one I have.

[Bill George]

When I had a limited amount to do under my pickup I found a needle scaler worked fine. No sandblasting near moving parts!