Galvanizing
Posted By : Kevin Rochfort, 09-Sep-2005, 12:30pm
Paul,
It's been suggested in the past that the heat involved in galvanizing might distort the chassis.
One would also need to ensure that there were sufficient drain holes in the right place to drain all traces of the acid dip, and also to allow the molten zinc to enter inside the chassis rails - and then drain out again whilst still molten as the chassis is removed from the bath - if the zinc solidifies as the chassis is draining it will block the drain holes and lead to a very heavy chassis !!!
If you want to pioneer the process, please let us know the results and the tricks necessary to get it correct.
Kevin
It's been suggested in the past that the heat involved in galvanizing might distort the chassis.
One would also need to ensure that there were sufficient drain holes in the right place to drain all traces of the acid dip, and also to allow the molten zinc to enter inside the chassis rails - and then drain out again whilst still molten as the chassis is removed from the bath - if the zinc solidifies as the chassis is draining it will block the drain holes and lead to a very heavy chassis !!!
If you want to pioneer the process, please let us know the results and the tricks necessary to get it correct.
Kevin
-
Galvanizing
Posted By : Keith Dandridge, 09-Sep-2005, 12:48pm
I'm modifying a Fiat 500 head as we speak, but the thought of it hauling a fully galv'd
body around is quite distressing.
Galvanizing
Posted By : Paul Southwell, 25-Oct-2005, 10:33pm
I am hopefully getting my chassis galvanized tomorrow, luckily my boss was good enough to let me acid clean and then shot blast mine at work over the
weekend. As it turned out it was a good job he did because shot blasting showed up a lot of defects that would probably have gone unnoticed.
The price I have been quoted is &163;70 +vat, but that might be a bit cheaper due to the chassis being ready to dip , as for distortion I will let you know how I get on .
(I got the chassis on eBay for &163;22 so it&194;&8217;s worth the risk)
The price I have been quoted is &163;70 +vat, but that might be a bit cheaper due to the chassis being ready to dip , as for distortion I will let you know how I get on .
(I got the chassis on eBay for &163;22 so it&194;&8217;s worth the risk)
-
Galvanizing
Posted By : Mark Stradling, 26-Oct-2005, 00:13am
Have you got time/space/inclination to pop it on some axle stands in the garage and take a few measurements?
So long as you don't move the stands, and can remember/work out exactly where the stands touched the chassis you will be able to see if/how much/where it's twisted when it comes back (and then bounce on bits to get it back to true ^_^) -
Galvanizing
Posted By : Stephen Airey, 26-Oct-2005, 07:46am
I am really interested in how this turns out. For kit cars it is 'de rigeur' to get the chassis galvanised so I doubt you will have problems - though ensuring sufficient holes is a good idea. I would be very interested to know how this turns out as I would also be interested in doing it on my next project (which will start as soon as I move into the new house with 8m * 4m garage !! yipee). 70 quid seems really cheap - I expected this to be around 400 quid. Definitely worth trying - and then telling the rest of us how and where to do it too!!
-
Galvanizing
Posted By : Jonathan Binnington, 26-Oct-2005, 07:52am
I had the chassis on my yellow GT6 hot-dip galved, the trick is to get it thoroughly cleaned in the first place.
a million landrover front bumpers ahve been made this way, not sue about hot-dip galving an entire body tub... might just need to do the bottom 6-12 inches, ever seen wings rust through at the top??
j-
Galvanizing
Posted By : Colin Wake, 26-Oct-2005, 08:16am
Sadly, yes!
From the inside out.....
Colin-
Galvanizing
Posted By : John Davies, 26-Oct-2005, 01:47pm
All,
Has anyone tried the 'sacrificial anode' style of zinc protection, that boaties use? Big lump of zinc bolted to the keel. In effect, the iron/zinc/electrolyte are a battery and as long as there is electrical continuity between the zinc and the steel/iron, the zinc is corroded, not the iron, until the zinc has gone. This is what galvanising does for a steel panel, I thought.
I know that boats are immersed in electrolyte - salt water - but in winter our cars might as well be in the sea for all the salt on the roads.
John-
Galvanizing
Posted By : Mark Stradling, 26-Oct-2005, 01:57pm
Galvanizing works in a slightly different way.
Zinc is a very reactive metal and oxodises really easily/quickly. Zinc Oxide (Zinc "rust") on the other hand is a fairly inert material.
Right out of the galvanising dip the surface layer of Zinc "corrodes" to perform a Zinc Oxide shell that prevents any water/ait gerring to the lower layers of Zinc, or the Steel behind it.
If you bash the galvanised item you can chip the Zinc Oxide outer coating off (quite easily actually - it's reasonably brittle). This only exposes some raw Zinc... that oxodises to form Zinc Oxide.
If you paint a galvanised item then the paint will protect the Zinc Oxide layer from breaking and so things should last even longer.
Ahh, 4 years at Uni. weren't wasted
-
Galvanizing
Posted By : Kevin Rochfort, 26-Oct-2005, 02:09pm
Here are a couple of pages of info on Hot Dip Galvanizing - they make interesting reading for those that either spent too long in the bar during their time at university, studied a different subject, or never went in the first place !
http://www.corrosion-doctors.org/MetalCoatings/Gal...
http://www.metalplate.com/galvanizing/ti.htm
-
Galvanizing
Posted By : Mark Stradling, 26-Oct-2005, 02:22pm
The Zinc Oxide layer is much more important than the electrolitic protection.
It sure ain't the electrolitic protection stopping lamp posts rusting!
I can bore for England on the topic of manufacturing household electric plugs and screws too (though the UK plug is much more interesting and one of the best designed objects you will find).-
Galvanizing
Posted By : John Davies, 26-Oct-2005, 06:25pm
Thank you, Mark & Kevin, for educating me!
As an aside, I have some thin, galvanised sheets that I don't like to use - the zinc peels off a cut edge and the raised zinc is VERY sharp. Does this mean that the galvanising is faulty? - according to one website, the zinc layer should be chemically bonded to the steel below.
John
-
Galvanizing
Posted By : Philip Brammer, 26-Oct-2005, 07:16pm
Hand up...I have a question please! I always thought galvanised steel worked by the zinc (?) loosing molecules of oxygen to the water. Eventually the galvanising runs out of oxygen and then the steel itself rusts, thats why corrigated galvanised steel sheets eventually rust. Is this something like or, like with Santa and the tooth fairy, must I be disappointed once more?-
Galvanizing
Posted By : Jonathan Binnington, 26-Oct-2005, 10:01pm
I'm intrigued, exactlty what was Santa up to with the tooth fairy? Hide the molar or somesuch??-
Galvanizing
Posted By : Philip Brammer, 26-Oct-2005, 10:07pm
I think the reply must include 'Bah, humbug'!
-
-
-
-
-
-
-
Galvanizing
Posted By : Andy Vowell, 26-Oct-2005, 09:45pm
Zinc anodes on boats work because with all the different types on metal on a ship the seawater acts as an electrolyte so a current is set up between things like the bronze propellers/seainlets and the steel hull, like a big battery. The steel hull is the positive terminal (anode) and the more exotic materials the negative (cathode). As current flows from the steel to the bronze it takes metal with it causing disimilar metal corrosion. The sacrificial zinc anodes replace the steel as the positive terminal so reduce this type of corrosion. On the ships I've worked with we replace about 1400KGs of Zinc every 5 years (ish)
(excuse the gross material generalisations, my Naval Architecture course was a little while ago)
As most spits don't sit in a solid bath of water all the time then this sort of corrosion is not really an issue, ie no water - no current, like when your battery runs dry.
So though a great bit of lateral thinking, sacrifical anodes would not really do the job, except maybe for an Amphicar.
Andy
-
-
-
-
Galvanizing
Posted By : Paul Southwell, 26-Oct-2005, 09:59pm
I dropped the chassis off this morning and got chatting to a man who once had a herald, and because he worked there he got his chassis dipped with no problems apart from having to re tap a few holes, also watch out for any brazed items because of the temp of the molten zinc the braze will melt and parts will drop off, on my chassis the brackets that the hand brake cable runs thro were brazed so I added some good tacks of weld on to them so they stayed put.
The price I was quoted was given by weight , 60-80 kg was &163;70 +vat and the chassis only weighs about 60kg , mind you that was on the bathroom scales and believe me its not easy carrying a chassis up the stairs to the bathroom (only joking)
As far as I know there could be extra charges for drilling holes to let the zinc drain out but I shall have to wait and see.
It should be done in the next few days
I will keep you posted
-
Galvanizing
Posted By : Paul Southwell, 03-Nov-2005, 10:21pm
Collected chassis today from East Anglian Galvanizing Ltd Peterborough. The first time they tried to dip the chassis it floated, so they phoned me to go and have a look at where a few small holes could be added to allow the zink to flow through some of the sealed box sections.
After a few holes were drilled in the appropriate places it was re dipped successfully.
When I got it home it did need a few drips and splashes of zink removing and the threaded holes in the chassis need tapping out .
It doesn&8217;t seem to have distorted in any way , although it did gain a bit of weight.
It weighed about 60kg before it was dipped , now it weighs nearly 70kg , quite a big weight gain , I think maybe some excess zink is in the box sections although they do all sound hollow , unless that&8217;s how heavy two dips in the zink weighs, who knows .
Anyway at all turned out ok and only cost me &163;85.25
Galvanizing-
Galvanizing
Posted By : John Davies, 03-Nov-2005, 10:27pm
Paul,
For a road car, 10kgs is nothing, and doesn't that chassis look good!
If you have the reprint Spitfire 'Reapir Operations Manual' it includes exhastive detail on squareness checking and dimensions.
Pages 76.10.02
John -
Galvanizing
Posted By : Mark Stradling, 04-Nov-2005, 10:29am
Ummm, shiny.
Looking really good. Slightly worried by the 2 hammers in shot but... ^_^
-
-
-