Rust prevention

[youngun]

With all the cutting, welding etc that will be taking place over the next few months, I think it may well be a good idea to paint the underneath and indeed all the new sections etc to stop the rust from creeping back again! Being right near the sea, rust can occur in a matter of hours round 'ere.

I have most likely opened a can of worms here, but what does everyone use to stop the rust, and that acts as a suitable base coat which can be sprayed over with topcoat where applicable?

thanks
YG

[paulhumphries]

I've had good results with cold galv spray.
I used to get commercial stuff used in construction industry for coating the welded joints on steel framed structures but no longer have the contact.
A car I restored nearly 20 years ago is still rust free despite being used everyday for many years and has topped over 250,000 miles (150,000 since body restored).
I now use this from Screwfix -
http://www.screwfix.com/app/sfd/cat/pro ... 4&ts=23578
Not as good as the commercial stuff (which was a LOT dearer) but still quite good if item coated is totally rust free.

Paul Humphries

[chickenjohn]

yes, Zinc paint as the primer layer is a very good idea! You can also get brushable zinc primer by the litre from your local auto paint factor. When the two coats of zinc primer are dry I then seam seal any welds or joints, when that is dry, then the topcoat- I used to use two coats of smooth rite, but now prefer the Chassis black paint.

When thats all dry, my obsessive rust proofing regime then involves a thicker underbody wax and the thinner wax rustproofer for inside box sections sills, etc. Re-apply the waxoyl/dinitrol regularly.

Like you, i live by the sea side , there are downsides as well as upsides, Yes, some salt in the air can be whipped up by an onshore wind, but during the winter, much less risk of frost so the council grits the road much less than inland.

[youngun]

Thanks John, Paul.

Round my way, im more worried about the corrosive properties of cow errrr droppings.....As i have to venture past 3 farms to get out of the village!

[Kevin]

im more worried about the corrosive properties of cow errrr droppings

Well glad thats not a problem I have

[Orkney]

Can highly recommend Galvafroid
http://www.wrmeadows.com/wrm00040.htm
used to use this years ago for general fabrication work, amazing stuff.
Very very zinc thick, you know it the moment you pick up the tin as its disproportionately heavier.
There are also some excellent zinc rich primers in aerosol cans now - these are best sourced from your local welding supplies company as they will be for industrial application rather than domestic and generally that = a far better product.
Not as good as the galvafroid but a darn sight easier to apply on larger areas.

[paulhumphries]

Can highly recommend Galvafroid
http://www.wrmeadows.com/wrm00040.htm
used to use this years ago for general fabrication work, amazing stuff.

I get proper hot galving done for free.
It's not the best firm as their "bread and butter" work is farm items where cheapness is prefered over quality.
If they have an area where the galv doesn't stick they use the same Galvafoid paint which shows how good it is !

Paul Humphries

[Orkney]

Heres a comparison of how good it is compared to other products in the outside environment here.
Japanned black hardware lasts approx 2 years
Plated - 3-4 years
Screwfix type (not proper industrial hot dip) galvanised 4-5 years
Galvafroid 15 years and counting

Thats just on general visible hardware - hinges gate fittings etc, goes to show how good it is.

[paulhumphries]

Heres a comparison of how good it is compared to other products in the outside environment here.
Japanned black hardware lasts approx 2 years
Plated - 3-4 years
Screwfix type (not proper industrial hot dip) galvanised 4-5 years
Galvafroid 15 years and counting

Thats just on general visible hardware - hinges gate fittings etc, goes to show how good it is.

Have you ever coated an item with Galvafoid and then welded it ?
The reason I ask is I always use cold galv spray on new panels etc which are being sealed (sills, chassis legs etc) and impossible to paint after intallation.
The commercial paint I used to get was so good you could weld though with very little burning off of the paint.
The Screwfix type splatters when heated even though dry (days / week rather than hours) so needs cleaning off at weld points.
It's still quite good at staying attached with again little burning from conducted welding heat.

Paul Humphries

[chickenjohn]

Frost do a weld thru primer thats much better for this purpose than the Screwfix type- though its expensive. You don't have to use Galavafroid brand, any heavy high zinc content primer will do an excellent job of protecting the underside of your car when used as a primer. It still needs a top coat and preferable wax on top as well.

I also had problems with the Screwfix zinc primer lifting and crazing when stone chip was applied, but the paint factor Zinc primer was fine.

I've got some weldable cold galvanising spray from Toolstation- as with everything they are cheaper than Screwfix and when sprayed it looks like the Frost product- shiny zinc rather than dull grey- only half the price. i'll let you know how it does when I do the sills on the other side of the current project.

[Orkney]

Have you ever coated an item with Galvafoid and then welded it ?

No never have - only used it as a coating where hot dipped galv has been cut/welded then added as the rust preventer before the steel oxidises.
In all fairness dont think i would ever use it in a situation where further welding was required in the forseeable future.

[alex_holden]

Presumably you have to wear some kind of breathing apparatus when welding metal that's been painted with weld-through zinc primer?

[paulhumphries]

Frost do a weld thru primer thats much better for this purpose than the Screwfix type- though its expensive. You don't have to use Galavafroid brand, any heavy high zinc content primer will do an excellent job of protecting the underside of your car when used as a primer. It still needs a top coat and preferable wax on top as well.

I also had problems with the Screwfix zinc primer lifting and crazing when stone chip was applied, but the paint factor Zinc primer was fine.

I've got some weldable cold galvanising spray from Toolstation- as with everything they are cheaper than Screwfix and when sprayed it looks like the Frost product- shiny zinc rather than dull grey- only half the price. i'll let you know how it does when I do the sills on the other side of the current project.

I've got loads of the Screwfix paint - I use it to make up orders to free carriage amount.
They seem to have changed the label but I don't know if the contents are by the same manufacturer.
A agree that it isn't the best of it's type but find that if a top coat is applied then it isn't too bad - certainly far better then ordinary primer.
Personal experience shows it sticks better on cleaned rusty metal (sandblasted, sanded, acid dipped) than new steel.
I also soak tins in warm water before shaking as I've had problems with splatter / blocking of spray button due I assume to the solids seperating out in storage.
As you say most paint factors can supply a zinc rich paint that I use for large underbody areas. Not cheap but brushable so goes a long way.
Paint factors can also supply proper chassis paint. I don't know how it differs to ordinary paint but it seems to be more resiliant to stone chips when used on suspension components.
Agricultrual merchants normally stock paint that is tough when used on machinery.

Paul Humphries

[dunketh]

I paint mine once a year with Hammerite underbody seal. Its got waxoyl in it. I use normal cavity wax (whatever brand I can find) for the internal stuff.

You wont find saltier air anywhere in the country than here so it does work but it will need at least an annual inspection.

[paulhumphries]

Presumably you have to wear some kind of breathing apparatus when welding metal that's been painted with weld-through zinc primer?

Despite a garage I always weld outside and have never had problem with fumes - any more than welding clean metal.
I've welded zinc sheet and that is horrible even if the "contact" points are ground off so I understand perfectly what you mean but the zinc paint doesn't burn off so it's only a very small area that would be affected ie a 10mm spot if plug welding.
Still probably best to wear protection, like you say, if doing a large area at once or inside a garage.


Paul Humphries

[paulhumphries]

Anyone seen the Bilt Hamber advert in Practical Classics ?
They have a test which shows effectiveness of their product against others -
http://www.bilthamber.com/dynaxs50comparison.html
I can guess "UK’s leading anti corrosion wax" is Waxoyl but what is the "Acclaimed Swedish Cavity Wax" ?


Paul Humphries

[Kevin]

I can guess "UK’s leading anti corrosion wax" is Wa

Hmm I thought that title went to Dinatrol in an older test, but Waxoyl is probably the most wildly used.

[alex_holden]

I thought both Waxoyl and Dinitrol were from Switzerland?

Waxoyl is probably the most wildly used.

ETA: I just checked and Dinitrol is made by a Swedish company called Dinol.

[paulhumphries]

I can guess "UK’s leading anti corrosion wax" is Wa

Hmm I thought that title went to Dinatrol in an older test, but Waxoyl is probably the most wildly used.

I think Waxoyl is the UK's most used rustproofer but Dinatrol is better in tests.
I've used both and think Dinatrol has the edge but the additonal cost means it's cheaper to regulary Waxoyl instead to provide same protection.

I was once offered a Herald where the owner had welded up every surplus hole in the mint chassis- and completey filled it to the brim with oil !

Paul Humphries