blakep82
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| posted on 8/6/12 at 10:50 PM |
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galvanic corrosion, here's a thought...
been thinking about this on and off for many many years, since high school chemistry really...
as i understand, cars are negative earthed so that the chassis is connected to the negative battery terminal, which helps prevent the chassis
corroding.
boats have zinc anodes on their steel hulls to help with the same.
galvanised steel is zinc coated to help prevent corrosion
I have a chandlry shop near me that sell zinc plates for bolting to boats, all sorts fo sizes available
i'm thinking about getting a small bit of zinc to fit to the chassis, hopefully it'll help stop the chassis rusting if the paint is
chipped, and its that far down the index, it should also help stop aluminium corroding too, and shouldn't affect the battery either
worthwhile? have a lot of peopl ebeen missing a trick? or is it going to be a waste of time, money, and a bit of extra weight (the weight
doesn't really worry me tbh)
any thoughts?
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liam.mccaffrey
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| posted on 8/6/12 at 10:59 PM |
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not sure you can remotely protect other parts of a stucture like that without an electrolyte?
EDIT
I'm no expert on cathodic protection, but the only times ive seen sacrificial zinc anodes is where there is an electrolyte/fluid.
[Edited on 8/6/12 by liam.mccaffrey]
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blakep82
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| posted on 8/6/12 at 11:06 PM |
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my thinking was that there would be an electrolyte present (salty water) to cause rusting in the first instance?
so it perhaps wouldn't be absolutely perfect all the time, but even if some of the time, then it would be ok?
________________________
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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D Beddows
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| posted on 8/6/12 at 11:07 PM |
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It's a theory - and possibly something you could successfully market on ebay with a bit of suitable 'snake oil' packaging  -I was
stood at the checkout in my local JTF discount warehouse a couple of weeks ago and some muppet was buying 5 things you plug into the cigarette lighter
socket in your car which were 'guaranteed to increase your mpg by 10%' for 3 quid + vat each for example - will bolting a small piece of
zink to your chassis actually significantly help combat corrosion............no
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Ben_Copeland
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| posted on 9/6/12 at 06:59 AM |
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They work on boats because it's sat in salt water... Cars arent, so its not going to do anything except add weight !
Ben
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adithorp
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| posted on 9/6/12 at 07:37 AM |
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quote:
Originally posted by D Beddows
...some muppet was buying 5 things... 'guaranteed to increase your mpg by 10%' ...
What a muppet! Just because one saves 10% doesn't mean 5 will save you 50%... or is that not what you mean?
...and Blake, NO it won't work, unless you stand your car perminently in salty water, which kind of defeats the object.
"A witty saying proves nothing" Voltaire
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matt_gsxr
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| posted on 9/6/12 at 08:10 AM |
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I can't see it working (because there isn't a complete electrical circuit, unlike when you have a boat in salt water).
The test would be to do it and see if the anode gets any smaller/lighter with time.
I have used galvanised bolts in places and my experience is that the zinc doesn't disappear (at least not quickly).
So my guess is "no".
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designer
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| posted on 9/6/12 at 08:28 AM |
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They sold plates to attach to your car for this in the 50's.
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avagolen
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| posted on 9/6/12 at 08:36 AM |
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They put them on boats in fresh water as well - so if you drive a lot in the rain 
The Answer for everything, but never the last word....
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daviep
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| posted on 9/6/12 at 09:38 AM |
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quote:
Originally posted by blakep82
been thinking about this on and off for many many years, since high school chemistry really...
i'm thinking about getting a small bit of zinc to fit to the chassis, hopefully it'll help stop the chassis rusting if the paint is
chipped, and its that far down the index, it should also help stop aluminium corroding too, and shouldn't affect the battery either
any thoughts?
I think your high school chemistry is letting you down, the anode has to be higher in the reactivity index, aluminium is above zinc in the reactivity
series so the aluminuim will actually protect the zinc.
You're only other option would be to use a magnesium anode.
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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blakep82
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| posted on 9/6/12 at 10:06 AM |
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hmm, well I never passed chemistry  i was going on holiday, and check in closed the same time as the exam finished, so you can work the rest out
gourock and greenock are very damp and slaty tbh. I live right next to the clyde, roads are still salty from winter, and it rains a lot. greenock is
allegedly the wettest place in scotland, although the same seems to go for dalness in glen etiv, so i suspect its up near the top at least, this town
seems to be an electrolyte... any cars i've ever bought have gone rusty pretty quick here
so, zinc is the wrong side of the chart, how does galvanised steel work to protect the steel? or zinc primer?
like i said, was just a thought, but i'm even more confused as to how galvanised chassis's for landy's and other stuff works now. i
know galvanised steel is completely coated in zinc, but i'd have thought it might still help.
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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daviep
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| posted on 9/6/12 at 10:19 AM |
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Zinc is above Iron but below Aluminium
Please - Pottasium
Send - Sodium
Little - Lithium
Charlie - Charlie
McLean - Magnesium
A - Aluminium
Zebra - Zinc
If - Iron
The - Tin
Lean - Lead
Horse - Hydrogen ??????? Cant remember why this is here
Cannot - Copper
Munch - Mercuray
Sweet - Silver
Grass - Gold
Properly- Platinum
That's how I was taugh to remember it at school (18 years ago).
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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Chippy
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| posted on 9/6/12 at 04:06 PM |
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quote:
Originally posted by daviep
Zinc is above Iron but below Aluminium
Please - Pottasium
Send - Sodium
Little - Lithium
Charlie - Charlie
McLean - Magnesium
A - Aluminium
Zebra - Zinc
If - Iron
The - Tin
Lean - Lead
Horse - Hydrogen ??????? Cant remember why this is here
Cannot - Copper
Munch - Mercuray
Sweet - Silver
Grass - Gold
Properly- Platinum
That's how I was taugh to remember it at school (18 years ago).
Cheers
Davie
Can't work out what Charlie is doing there either! (Copper) Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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Paul_C
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| posted on 9/6/12 at 05:12 PM |
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I was under the impression that zinc plated steel works because the zinc forms an impervious oxide quickly sealing the steel.
Also I have heard but don't fully understand that it is a 'sacrificial anode' so corrodes before the steel. So for the boat the zinc
anode corrodes first. But you need an electrolyte so I guess that the boat zinc anode only protects the part underwater. Steel above the water and on
the inside aren't protected.
I remember reading about the idea being suggested for cars a couple of decades ago. If it worked I guess people would be using it though in my
experience modern cars are far better painted that the cars of the 60s and 70s. I remember my 1975 Rover being decidely crunchy and tatty in 1984 when
I crashed it.
I would have fears about galvanising complete chassis because the dip in the molten zinc might cause distortion. It certainly used to twist the
conveyer frames were I worked many years ago.
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RichieW
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| posted on 9/6/12 at 05:49 PM |
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Can't work out what Charlie is doing there either! (Copper) Cheers Ray
I think Charlie is Calcium as it is at the reactive end of that list. Copper would be down the other end.
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daviep
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| posted on 9/6/12 at 06:49 PM |
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Doh........Charlie should indeed be Calcium 
“A truly great library contains something in it to offend everyone.”
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