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How effective is pressure washing for rust?


EdHopwood

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hello there, here's my second question for any of you kind people who'd like to help after the great help I recieved last time. So i've scraped all the rust from the inside of my Hull and I'm ready to paint. Iv'e started to pressure wash an area on my neighbours advice then suck the water out. Very messy but I needed a shower anyway:) On a serious note though, is this the best way to get rid of the rust? Do I know just paint with Zinc Oxide paint?

 

kind regards Ed

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hello there, here's my second question for any of you kind people who'd like to help after the great help I recieved last time. So i've scraped all the rust from the inside of my Hull and I'm ready to paint. Iv'e started to pressure wash an area on my neighbours advice then suck the water out. Very messy but I needed a shower anyway:) On a serious note though, is this the best way to get rid of the rust? Do I know just paint with Zinc Oxide paint?

 

kind regards Ed

 

At least you know that you have clean rust now!!! :rolleyes:

 

As long as you no longer have any thick or loose rust, and have got rid of as much of it as you can, (although washing with a jet wash will guarantee that all clean metal will now have a thin film of rust on it of course!) - then you can now start your painting with your preferred paint(s)

 

Just remember - - particularly when you are painting your superstructure (I realise that you're doing the inside of your hull at the moment - and you aren't after a mirror finish!) - - do not let anything contaminate your painting surfaces - not solvents, not grease, not hand/fingerprints, not dog paws (etc etc) and keep your job as clean as you possibly can

 

Enjoy!

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Can't help thinking that you'd have been better off scraping, wire brushing and then hoovering out the residue........

Dryer, less messy, no drying out and then wire brushing before priming.

what does something like vactan do in this situation, and how to apply and what to do afterwards?

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At least you know that you have clean rust now!!! :rolleyes:

Just about sums it up, really.

Unless you go back to clean shiny metal, and start again from that, then whatever you stick over it will simply trap any molecules of water and acerbate the problem.

Edited by Dog
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Well - - at least Vactan will have a thin rust film to activate - but I'm sure the hull will need to be perfectly dry to apply it (by brush)

 

 

I believe Vactan can be applied to damp steel/rust.

 

Ian

 

Just about sums it up, really.

Unless you go back to clean shiny metal, and start again from that, then whatever you stick over it will simply trap any molecules of water and accerbate (sp?) the problem.

 

 

 

Does Vactan not react with the moisture in the rust and stop further problems?

 

 

Ian

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hello there, here's my second question for any of you kind people who'd like to help after the great help I recieved last time. So i've scraped all the rust from the inside of my Hull and I'm ready to paint. Iv'e started to pressure wash an area on my neighbours advice then suck the water out. Very messy but I needed a shower anyway:) On a serious note though, is this the best way to get rid of the rust? Do I know just paint with Zinc Oxide paint?

 

The cleaner the surface the more likely the paint is too stick, you don't want any oil residue on the surface so I use a jet wash as well, but I also use a cleaner like marine clean after jet washing to clean the rust/metal/paint as well (then jet wash and hose rinse that away).

 

To dry it I use a dehumidifier, fans and a window rubber blade thingy - what ever there called.

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Thanks for all your quick responses. Much appreciated for a woodworker like myself who's trying his luck with steel!

I'm a bit confused though, I've been told if you pressure wash the loose rust off then the paint will deal with the rest and if it blisters up you just keep giving it the same treatment. is this the case or am I just covering up rust that will continue to eat away at the steel? I also don't really want to do it twice. Are the alternatives to shot blast(not really an option) or try and grind everything back to bare steel? (angle grinder with wire brush??)

 

cheers Ed

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Yes, Vactan can be applied to damp (not sopping wet) rust.

 

Just been researching vactan, maybe that's the way forward. Do I just use standard metal paint after that as the vactan eliminates the need for the Zinc Oxide paint though?

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Thanks for all your quick responses. Much appreciated for a woodworker like myself who's trying his luck with steel!

I'm a bit confused though, I've been told if you pressure wash the loose rust off then the paint will deal with the rest and if it blisters up you just keep giving it the same treatment. is this the case or am I just covering up rust that will continue to eat away at the steel? I also don't really want to do it twice. Are the alternatives to shot blast(not really an option) or try and grind everything back to bare steel? (angle grinder with wire brush??)

 

cheers Ed

.

Ed- sorry mate, but to get rid of rust you have to completely eliminate it. Sandblasting/shotblasting is the best way to go

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Apparently the neat holes in the hefty angle iron supports for my Lister were cut with water jet. I think maybe some abrasive is added to it though.

 

Imagine using something like that to clean off the rust :o

We use to cut pipelines with inch thick walls with water jets

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<snip>

 

is this the case or am I just covering up rust that will continue to eat away at the steel?

 

<snip>

 

cheers Ed

 

Rust is iron oxide, formed by the combination of the oxygen dissolved in the water and the iron in the steel of your hull. So, if you trapped some water under paint, once the oxygen is combined in iron oxide, it is no longer available to make rust

 

However, iron oxide is about ten times the thickness of the original iron, and is porous. So, the key question is, has the rust formed caused fractures in the paint to allow more oxygen in? Removing as much rust as you can and keeping it dry before applying an effective paint seal is the way to go. No oxygen, no rust

 

Richard

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Rust is iron oxide, formed by the combination of the oxygen dissolved in the water and the iron in the steel of your hull. So, if you trapped some water under paint, once the oxygen is combined in iron oxide, it is no longer available to make rust

 

However, iron oxide is about ten times the thickness of the original iron, and is porous. So, the key question is, has the rust formed caused fractures in the paint to allow more oxygen in? Removing as much rust as you can and keeping it dry before applying an effective paint seal is the way to go. No oxygen, no rust

 

Richard

 

The 'effective paint seal' is the critical bit. It's no good just slapping on a coat or two of primer, you have to use something which will firstly adhere to the rusty surface and secondly not be porous.

There are paints which claim to be suitable for applying direct to rust, such as Rustoleum and Hammerite, I presume they combine an ability to bond to rusty surfaces with minimal porosity, but the more rust you can remove the better the long term results are likely to be.

 

Tim

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