Stainless steel bolts... - MG-Rover.org Forums
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post #1 of 24 (permalink) Old 13-05-2017, 14:09 Thread Starter
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Stainless steel bolts...

I see a lot of you guys replacing mild steel bolts with stainless steel equivalents.

I was always led to believe that stainless and mild steel react and corrode excessively...

Is this wrong or am I missing something?
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post #2 of 24 (permalink) Old 13-05-2017, 14:25
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Not had any issues with any stainless I have fitted, tbh stainless bolts are advisable in certain areas and not in others, particularly where high stresses are found.
I would most certainly fit stainless under the bonnet for things like front bumper and under bonnet hardware, most definitely for the anti lock brake sensors, because they always seize solid and you end up either rounding the bolt off or snapping it.
I would also consider fitting to things like the alternator bracket and exhaust flanges etc.


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post #3 of 24 (permalink) Old 13-05-2017, 14:56
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SS still rust, as I've found out, even rather quickly, but looks good longer
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post #4 of 24 (permalink) Old 13-05-2017, 19:30
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there are many grades of stainless steel. some can resist 95 percent sulphuric acid ... for example.. you need to look up the grades, and choose your method. based on the qualities. would be my advice, not least the electro chemical reaction of stainless steel when in contact with mild steel.. because the stainless accelerates the reaction ... and the mild steel suffers more...

so you might have a great stainless bolt secured to a quickly rusting hole...

there is the reason that many minor fixings to panels use plastic inserts, because it negates the point of contact reaction... the plastic is an insulator.

its important.. to remember the whole car... is an electrical resistance circuit.. and where there is even a minor potential difference.. a reaction occurs when those points are conductive.


of course .. time is your friend... some reactions take a long time to become a negative consequence.. to the user...

Last edited by Incony; 13-05-2017 at 19:42.
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post #5 of 24 (permalink) Old 13-05-2017, 20:09
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I've used marine grade SS bolts and long (cat saver) nuts on my SS exhaust system - much easier to get things disassembled and no signs of any corrosion yet after 2 years. After hearing horror stories about how people suffer trying to replace catalytic converters etc, I thought it would be wise to make sure that it would be as easy to take apart as possible for future.
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post #6 of 24 (permalink) Old 14-05-2017, 09:51 Thread Starter
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I just wondered what people's experiences were.

As an apprentice electrician I changed out an old field marshalling panel in a paper machine underdrive, a very damp and warm area.

The engineer supplied a new stainless panel with new SWA cable glands fitted, secured to the panel with mild steel lock nuts.

Within a year, the bottom of the stainless panel had corroded.

I just wondered if people had seen anything similar.
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post #7 of 24 (permalink) Old 14-05-2017, 16:06
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As Incony states, stainless steel is graded and higher chromium content will weather better than the lower grade stuff.
My TT mk.7 exhaust is stainless and was fitted at Christmas time, it is already showing signs of rust on the bottom of the boxes!


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post #8 of 24 (permalink) Old 14-05-2017, 17:47
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There are many grades, The ones I use are A2 or A4.


Use a magnet some SS is slightly magnetic (has a small amount of ferrous)
If not magnetic, should be rust free.
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post #9 of 24 (permalink) Old 14-05-2017, 17:57
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Stainless steel is what it says. It stains less.
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post #10 of 24 (permalink) Old 14-05-2017, 20:04
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post #11 of 24 (permalink) Old 14-05-2017, 20:33
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yup... my point was that the higher nobler metal suffers less corrosion... and the lower, suffers more.

so if you bring stainless into contact with mild steel.. by say screwing a stainless bolt into a mild steel panel.. and add water... like rain or condensation.. whatever// then the mild steel will rust faster and more.. just because of that contact...

its a false premise that you get something for nothing.

And also, because you have set up a dissimilar resistance path... then every point surrounding it, will change its electrical conductivity.. and reaction... and become a radiating resistance path, just because your introduction a of two dissimilar metals has enabled it, at one point..

you turn on a light and the light shines into the shadows.. where there was no light before.


i have been involved in the weld testing of corrosive liquids in contact with welding of pipes in stainless steel.. and i can tell you the welds failed, because the content of the welds - accelerated reaction. the stainless pipe did not suffer at all.. but the welds at every joint failed because they were less noble.. and the pipes leaked

you only see the light you turned on... its your focus...

Last edited by Incony; 14-05-2017 at 20:51.
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post #12 of 24 (permalink) Old 14-05-2017, 20:43
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I change to SS where possible and use Dinitrol RC900 on almost everything else.
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post #13 of 24 (permalink) Old 14-05-2017, 21:10
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Quote:
Originally Posted by steviejones133 View Post
I've used marine grade SS bolts ....
This exactly

A high proportion of the stainless steel nuts and bolts readily available from the usual sources (ie principally eBay) are lower grade stainless, and will not stand up to exposure to salty dampness on a car for very long at all. I have also found that some suppliers of stainless add-ons for cars (such as gas strut bonnet lifters) also use an inadequate grade of stainless, which I find quite unbelievable.

I too have only ever used marine grade stainless (A4/316), and have had no issues with corrosion. However, the extra chromium content which gives the extra corrosion resistance has the negative side effect of making it more susceptible to fatigue and cracking, so wouldn't be recommended for use in higher stress areas or where long term strength is important.

Stainless is good for obvious nuts and bolts in line of sight (such as incidental fixings in the engine bay), where cosmetic appearance is important, but for major component fixings, it is probably better to use the correct tensile steel bolt and a good coating of anti-rust protection.
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post #14 of 24 (permalink) Old 14-05-2017, 22:10
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ToolStation are the best price but A4 are from ScrewFix.


I use the A2 for most applications (High Tensile where needed) , good enough for accessories/bodywork etc.


My engine:



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post #15 of 24 (permalink) Old 14-05-2017, 22:58
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I've tried what were supposed to be A2 in the past (underbonnet trim fixings), and they rusted very quickly. Perhaps some of what is sold as A2 on eBay may not be what is claimed?
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post #16 of 24 (permalink) Old 15-05-2017, 06:56
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Quote:
Originally Posted by Man in the Car View Post
... some suppliers of stainless add-ons for cars (such as gas strut bonnet lifters) also use an inadequate grade of stainless, which I find quite unbelievable.
I've noticed myself.

I don't want to make names, yet, but any uprated parts advertised as SS bought from a certain MG specialist, are already rusty (very rusty) after a few months.
SS bolts bought on ebay from random seller, are shiny and looks as good as new.

I noticed this even more yesterday, when I replaced my anti-rollbar droplinks SS nuts with SS lock nuts.

Same with rose joints bought from this MG specialist and rose joint bought on random ebay seller.
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Last edited by DeathFromAbove; 15-05-2017 at 07:21.
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post #17 of 24 (permalink) Old 15-05-2017, 09:36
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don get me wrong. i too, use stainless steel fixings.. and its because they are likely to rust less, and be more likely to undue easily.

one only needs to see the reaction of the aluminium wheels with the steel wheel bolts to see the electro chemical reaction i talk about... the dreaded white powder ... aluminium oxide..

pretty much anything that comes into contact with water ( the activating agent ) will show similar reaction, and folks know that and deal with the results..

like.. seizing door window mechanisms, failing alternators... duff fuse connections,, bad earths,,, hood mechanism rust,,, and the growth of rust spots, and seized steel bolts, particularly those that go into aluminium.. or remain undisturbed

wherever possible i still use an insulator... to stop or reduce the reaction between dissimilar metals... like grease, or oil based lubricants, plastic insulators...
paint - etc... on any thing that doesnt rely on clean uninsulated contact - like electrical fixing points... those i just have to keep clean and maintain more regularly..

for those that like show cars.. dedicated time spent cleaning to make things shine.. isnt a problem.. bt my F sits oustside and is doing over 80 miles a day in all weathers... and until recently i was leaving home in the dark and getting home in the dark for the last 5 months plus.. 4 days a week.

so insulation is still my preference over metal to metal contact where possible.

and if one considered that the whole car body steel was so insulated by coating , before it was spray painted,,, and mine is still going strong, though beginning to show failure now.. after 17 years... then i think insulation wins where possible.
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post #18 of 24 (permalink) Old 15-05-2017, 11:09
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I think you are right and agree.

Metal alone is much more susceptible to corrosion.
On the other hand, I'm speaking of SS over SS, that become brown rusty, and looks worse than some bolts that where on the car by 16 years.

My droplkinks has been replaced by "high quality" SS rose joints , with associated SS bolts, SS nuts AND provided with rubber boots by me.

The bolt was SO rusty yesterday, the the nut had difficulty to unlock towards the end!
Something the old droplink didn't do, after 15 years!

I've changed to rose joints for the gear crank bell, bought by me on ebay as "high quality" and guess what: after the same amount of time they are still shiny!

The more I think of it... were these part SS at all?
Even the bonnet struts presents rusting, and should not bhe exposed to the same harsh environment than droplinks.

Last edited by DeathFromAbove; 15-05-2017 at 11:19.
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post #19 of 24 (permalink) Old 15-05-2017, 12:22
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If you replace nuts and bolts with SS hardware, make sure that the SS hardware is of the same grade as the original hardware because unless you ask for a specific grade, most has less strength.

Also, SS has a propensity to gall, so if you are install SS hardware in a place where you will be taking the hardware apart frequently, make sure antisieze to minimize galling of the threads and replace the hardware if you notice galling.
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post #20 of 24 (permalink) Old 20-05-2017, 07:05
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would giving the SS bolt thread a coating of copper grease slow down the galvanic corrosion, if a SS bolt/self-taper was used with a non SS fasteners?
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