does stainless react with galv

AntHughes · Apr 2, 2014

HI guys ive bit the bullet and currently in the process of getting a galvy chassis and sourcing new shiny bits to replace when I do the swap.

now the problem ive got is I was going to get all stainless bolts and fittings for the rebuild but have read recently that if stainless comes into contact with galv it will cause corrosion and will compromise the integrity of the zinc coating which in this case means my chassis.

just wondering if any body on here could shed some light on the situation, whether its bull, or any solutions, alternatives ????

now I read that you have to get bpz bolts rather than stainless, now ive never heard or bpz so im quite clueless at the min as to what to do ???

the_wolf · Apr 2, 2014

Don't use stainless on structural components. BZP bolts are zinc plated. Not rust proof but better than just plain old mild steel

The Mad Hat Man · Apr 2, 2014

stainless is fine on structural components - just need to get the correct stainless.

the_wolf · Apr 2, 2014

Ah most things I've read said not to use stainless on structural components. I stand corrected

trax · Apr 2, 2014

you are referring to bimetallic corrosion or galvanic corrosion. i'll let you google that.

the metal needs to be dissimilar, touching and have an electrolyte to corrode.

so either stop them touching or stop any electrolyte (salt water, humidity, rain, etc).

stuff like duralac can be used for dissimilar metals, then spray the exposed stainless with paint, or in your case cold galv.

or just use bzp, stainless isn't as strong as 8.8s. you can cold galv them to give greater protection.

oh, also coppaslip is an electrolyte.

if it were me, i'd just use bzp + coppaslip and paint over it to help protect. for alu, i'd use bzp and a non metallic washer and paint and keep an eye on it

ebbadger · Apr 2, 2014

mad hat man... what grade stainless is equivalent to 12.9 high tensile?? the strength of many landrover structural bolts?? I visited a lot of suppliers and did a lot of research when starting my rebuild and all said not available???

after a lot of digging I went down the bzp route and seems a good choice so far

cheers steve

listerdiesel · Apr 2, 2014

316 stainless is pretty good for dissimilar metal corrosion, and 304 is close.

We used a lot of stainless fasteners on the big trailer, and also on the previous twin-axle trailer, especially the M12 bolts to hold the axles to the chassis. Never had the whiff of a problem.

Wolf is correct in a way as stainless are not high tensile per se, if you must have high tensile for any reason, get steel.

Peter

AlbertDefender90 · Apr 2, 2014

Don't use stainless anywhere where strength is essential I.e suspension components as the majority of a2 and a4 bolts are weaker than 8.8 bolts. You can get quite strong stainless bolts but they are compromised on corrosion resistance so you may as well use bzp.

The Mad Hat Man · Apr 2, 2014

a lot of stainless fixings are used in the aircraft industry where strength and corrosion resistance is critical. But they are feckin expensive

. They dont tend to use much galvanised steel though

.
Galvanised steel uses zinc as a sacrificial anode to protect the base metal. Stainless steel will be cathodic to the steel, so it will be even more cathodic to the zinc, hence you will get enhanced corrosion of the zinc, so to answer your original Q - dont use stainless & galvanised steel..

AntHughes · Apr 2, 2014

Thanks guys

Tim4x4 · Apr 3, 2014

AntHughes said:
HI guys ive bit the bullet and currently in the process of getting a galvy chassis and sourcing new shiny bits to replace when I do the swap.

now the problem ive got is I was going to get all stainless bolts and fittings for the rebuild but have read recently that if stainless comes into contact with galv it will cause corrosion and will compromise the integrity of the zinc coating which in this case means my chassis.

just wondering if any body on here could shed some light on the situation, whether its bull, or any solutions, alternatives ????

now I read that you have to get bpz bolts rather than stainless, now ive never heard or bpz so im quite clueless at the min as to what to do ???

See attached may help for the future.

does stainless react with galv

AntHughes

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the_wolf

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The Mad Hat Man

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the_wolf

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trax

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ebbadger

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listerdiesel

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AlbertDefender90

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The Mad Hat Man

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AntHughes

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Tim4x4

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