Maintaining a Galvised Chassis ?

[Crofter]

My Land Rover 90 has a Galvinised chassis fitted, this is it's first winter on the road and Iam a bit alarmed by the change in apearance of the finnish, i was not expecting it to stay shinny, but it's getting a gray rough coating esecialy round the outrigger at the fuel tank. is this normal or do i have a problem. Is there anything I need to do to preserve the chassis, I know nothing lasts forever but I thought a galvinised Chassis would bear up better.

Any advice would be appriceated I have attached photos of the parts mentioned.

Thanks Ronnie

[dantd5]

I am thinking the salty roads has a play in this. I do regularly was under truck to avoid residue of salt linings on the chasis. In Norway the constant salting creates the sort of "map" you see on the pic!!An adult will come up shortly!!!

[jbs]

That's how my ones going too, there was a thread on here a while ago about looking after galvanised chassis's perhaps a search would help?

[tuko]

My galvanized frame has done the same thing after a few years of road grime.

In my eyes and what I've done is considered the frame as an unprotected steel frame, waxoyled it inside and out. Every year I thoroughly pressure was the frame and update the exterior with new waxoyl where necessary.

Todd.

[Crofter]

This chassis was new and this was the first winter on the road, it was ok until just before Chrismas, thats when we got real snow and the roads were salted, I knew there would be a deteriation in the finnish, this just seems quite severe. A guy at work has a series 2 with a galvinised chassis and it is the same all over as the worst places on mine, but it's quite old. Most of My chassis still looks good with a nice finnish it's just the bit's I photoed and the front legs that are gray and rough. I will waxoil mine in the spring when the salt is off the road as I don't want to waxoil salt in, I will use black waxoil for the exterior and clear for the inside.

Ronnie.

[MOJO90]

Galvanising is a form of sacrificial cathodic protection. Galvansing is hot dipping in metallic zinc. The zinc is more active than the steel chassis and 'corrodes' in preference to the steel - this is how it protects the steel. The rate of 'loss' (by corrosion)of the zinc depends on the corrosivity of the environment. Salt water is more corrosive then fresh water and so when there is a lot of salt on the roads the rate of loss of the galvanising will be greater. However, it is still only microns per year. Keep the rate of loss down by regularly washing with fresh water.

The other thing is that zinc forms 'soluble zinc salts' (known as 'white rust') when exposed to water and some of what you can see will be zinc salts and some will be surface loss of zinc as is intended but accelerated due to the strong salt water conditions.

The life of the chassis will depend on the thickness of the galvanising - once all this has gone then the steel will start to corrode but you are still looking at many years - far longer than steel on its own, and longer than the best paint system (and that's from a guy who specifies paint for corrosion control in the offshore oil industry).

In the paint industry we sometimes use so called 'duplex' systems of galvansing plus paint to extend the life of the galvansing. This does work as it slows down the rate of loss of zinc and extrends the life BUT galvanising is often not easy to paint successfully. Actually it is easier to get paint to stick to galvanising once it has been weathered BUT you need to make sure all the soluble zinc salts are removed with fresh water (not always that easy) - otherwise you can get osmotic blistering (blisters and lifting of the paint) over the salted zinc.

You can inject the box sections with Waxoyl and either the same or paint on the outside to extend the life of the galvansing but it will last a long time even if you don't. You may find that the paint comes away from the galvanising from time to time due to the salts I mention above - you will have to scrape back to firm edge and wash with clean water, dry & then reapply the paint in that area.

Hope this long reply is helpful.

[Drizz]

I have a galv chassis coming but want to paint it prior to fitting up. Whats the best paint to use?

[TD5 power]

hi

the process i have used on my new chassis is

1. apply mordant solution (T wash) this helps the paint bite into the surface
2. acid etch primmer from what i can find has to be sprayed to get good results
3. a couple of coats of normal grey primmer
4. one or two coats of high build black top coat

I've still got the final top coat to spray but should be done this week once thats done i will probably coat the inside of the rails with waxyoil, with all that done it should easily outlast the rest of the truck

HTH

matt

[rusty_wingnut]

mine was galv'd then zinc sprayed twice then powder coated (not that Britpart cheapo nonsense either)

a year later and it still looks as fresh as a daisy, used everyday too

[zoltan]

In the paint industry we sometimes use so called 'duplex' systems of galvansing plus paint to extend the life of the galvansing. This does work as it slows down the rate of loss of zinc and extrends the life BUT galvanising is often not easy to paint successfully. Actually it is easier to get paint to stick to galvanising once it has been weathered BUT you need to make sure all the soluble zinc salts are removed with fresh water (not always that easy) - otherwise you can get osmotic blistering (blisters and lifting of the paint) over the salted zinc.

How long do you reckon you'd need to leave a new galvanised chassis outside to weather sufficient for paint?

[hobson]

Can't you use Hammerite special metals primer to paint onto new galv? i'm sure thats what we put on the roof rack...

thats what it says on here: http://www.hammerite.com/uk/products/ps_special_metals_primer.html

[muddy4x4xfar]

hi im on with a project 110 defender its also got a galvanised chassis. i wanted it to be galvanised then black coated. i went to a auto paint shop and they also recommended hammerite paint. painted over the top of a primer. if you give it a good couple of coats with the primer and a few tins of hammerite paint it will be fine. iv done it that way and it looks awsome.

[MOJO90]

I'll try to pick-up a few posts at once.

I know this sounds daft but the best specification used is to 'sweep blast' the (new) galvansing then apply a 2-pack epoxy primer. We did a lot of research and found an epoxy MIO(Micaceous Iron Ore)to be best for adhesion (adhesion to new galvansising is difficult hence the sweep blast or T-wash surface preparation) but any good 2-pack epoxy primer will do. The sweep blast is done with a fine aggregate that is non-metallic under low pressure so as not to remove too much zinc - but I'll bet most of you won't want to do that to your shiny new chassis!

The next best system is to 'T-wash' (this is an acidifed copper sulphate solution)and can be bought from industrial paint suppliers. T-wash is best applied with a brush to 'work' it into the rough galvanised surface - if it has reacted properly the zinc will turn black. You need to wash off the excess T-wash after it has reacted with clean water and then allow to dry before painting. Then apply the 2-pack epoxy primer (1 or 2 coats) then the top coat (probably black would look best but your choice).

Other 1-pack paints can be used like solvent based vinyl paint (my wrought iron galvanised gate is painted with a vinyl paint by the guy who made it and it's stil OK a few years later) but DON'T use an ordinary alkyd paint (the solvent based glossy stuff you paint your internal house woodwork with. The metallic zinc can react with the alkyd paint and undergo a reaction called saponification (you get a soap like residue as the paint breaks down).

If you can get it powder coated then even better but it still should be properly pre-treated as above and make sure it's a proper epoxy powder system.

If the chassis is new then paint it while off the truck so as to get to all of it - once it's on it will be harder to do.

These are the best options but you can opt to just degrease the galvansing and apply the paint but it may flake off in places due to 'patchy' adhesion. Also if the paint is very thin and 'porous' then water will get to the zinc which will then 'white rust' pushing off the paint in time.

If the galvanising is 'weathered' - it shouldn't take very long especially under a vehicle on our roads (a guess but probably a month or two depending on time of year) - then the 'zinc salts' (see previous post) need to be washed off with fresh water, then allow to dry. In this case there is no need for T-wash. Suitable paints as above.

Despite all said about painting galvanising - if it is a good thick galvanised job then it will last for many years on it's own - the paint just helps extend the life so if it came off it would not be a disaster. Many may choose to leave it in the galvanised finish.

[Drizz]

I dont want mine to be obviously galvanised so when it arrives i want to paint it prior to fitting it up. Cheers for youre advice. Ill bookmark this for future reference!

[moore101]

Can't you use Hammerite special metals primer to paint onto new galv? i'm sure thats what we put on the roof rack...

thats what it says on here: http://www.hammerite.com/uk/products/ps_special_metals_primer.html

This is what we did on dads series one 7/8 years ago and its still on there, the black on top is starting to show signs of wear and could probably do with another coat but its still on there! Pleased with results and it helps hide the new chassis.

[ajh]

I painted with Zinc Chromate primer and top coated with Tremclad Professional semi-gloss. Will let you know how it holds up in a few years, our environment here is one of the worst for salt damage. I suspect that even so I will end up needing to spray it with some kind of wax product within the first 3 years. The advantage of wax vs paint is the flexibility, the harder the surface the easier it is removed by grit-blasting, so the same applies to road debris.