Does stainless cause problems
Discussion
I recently fitted a water pump using Stainless bolts with copper anti-seize grease. I mentioned this to a group of friends which resulted in much sucking of teeth, sharp intakes of breath and anecdotal tales of disaster. These Included “I knew a man who used stainless bolts on his motorcycle crankcase and when he got up in the morning the bike had dissolved into a pile of white dust” and “when this blokes land-rover got caught by the tide the only usable parts left were those attached to stainless bolts by copper grease” (I may have misquoted slightly – my memory is a little befuddled as at least the conversation was well lubricated).
This made me curious, and I’ve looked on the internet but I cant find definitive answers, though I have learned that the Permatex data sheet for their copper anti-seize recommends it for spark plug threads in aluminium heads, that a number of aluminium alloys actually include copper and that 304 StSt is a long way from mild steel in nobility. What I have really found are lots of different opinions that seem to be based only on theory..
I know many of the people on here use a lot of stainless. Do you use StSt bolts in aluminium type alloys, does copper grease act as an electrolyte, does the copper in the grease react with the aluminium, or act as a sacrificial anode, and is copper grease conductive. So many questions, so little time, does anyone know any answers?
And the most important question of all - has anybody ACTUALLY had any real first hand personal experience of problems with StSt bolts or copper anti-seize grease?
This made me curious, and I’ve looked on the internet but I cant find definitive answers, though I have learned that the Permatex data sheet for their copper anti-seize recommends it for spark plug threads in aluminium heads, that a number of aluminium alloys actually include copper and that 304 StSt is a long way from mild steel in nobility. What I have really found are lots of different opinions that seem to be based only on theory..
I know many of the people on here use a lot of stainless. Do you use StSt bolts in aluminium type alloys, does copper grease act as an electrolyte, does the copper in the grease react with the aluminium, or act as a sacrificial anode, and is copper grease conductive. So many questions, so little time, does anyone know any answers?
And the most important question of all - has anybody ACTUALLY had any real first hand personal experience of problems with StSt bolts or copper anti-seize grease?
Experience; motorcycle casings are aluminium alloys, it is almost universal practice to take out the relatively cheap bolts and fit stainless socket heaqd screws. All motorcyclists seem to have Copaslip on hand! My Hondas have had stainless screws and grease or copaslip for about 40 years, a damn sight less corrosion, no more seized or broken screws!
In the application you are talking about I wouldnt have any worries, certainly less problems than with the original steel bolts! Rusting steel bolts expand slightly and can get so tight that the torque needed to shift them exceeds the strength of the alloy casting, so the casting breaks.
That having been said stainless fixings need to be used with care. Where tensile strength, or resistence to regular changes in stress (brake mountings for example) are concerned then a great deal of care needs to be taken to select fixings which are suitable for those loads. 'Stainless' is a misnomer as it does corrode in some circumstances.
In the application you are talking about I wouldnt have any worries, certainly less problems than with the original steel bolts! Rusting steel bolts expand slightly and can get so tight that the torque needed to shift them exceeds the strength of the alloy casting, so the casting breaks.
That having been said stainless fixings need to be used with care. Where tensile strength, or resistence to regular changes in stress (brake mountings for example) are concerned then a great deal of care needs to be taken to select fixings which are suitable for those loads. 'Stainless' is a misnomer as it does corrode in some circumstances.
lewdon said:
Do you use StSt bolts in aluminium type alloys?
Yes.lewdon said:
does anyone know any answers?
Doubt it.lewdon said:
has anybody ACTUALLY had any real first hand personal experience of problems with StSt bolts or copper anti-seize grease?
No.If you're loosing sleep over it how about Stainless anti seize... and there's £25 off!
Edited by phillpot on Sunday 3rd April 06:42
lewdon said:
.......And the most important question of all - has anybody ACTUALLY had any real first hand personal experience of problems with StSt bolts or copper anti-seize grease?..
I replaced most of the bolts for attaching things to my engine in 2010 using SS and copperslip, and I still have everything attached and no corrosion. In fact, I occasionally have to tweak the manifold bolts to keep them tight!Ah, something I know about for once!
Yes, aluminum and stainless steel can and do corrode when put together and the environment that they are in will determine the speed that the reaction occurs. The two differing metals set up a galvanic couple (aka a small battery) and corrode. The aluminum loses.
Add in some moisture and the reaction happens faster.
Add in some other electrolyte or source of ions, like something acidic or basic or salty or etc, and the corrosion reaction will occur even faster.
So, totally dry and totally clean (anodized aluminum and passivated stainless steel) would last for a while.
But if you have any moisture or ions involved, the aluminum loses.
Yes, aluminum and stainless steel can and do corrode when put together and the environment that they are in will determine the speed that the reaction occurs. The two differing metals set up a galvanic couple (aka a small battery) and corrode. The aluminum loses.
Add in some moisture and the reaction happens faster.
Add in some other electrolyte or source of ions, like something acidic or basic or salty or etc, and the corrosion reaction will occur even faster.
So, totally dry and totally clean (anodized aluminum and passivated stainless steel) would last for a while.
But if you have any moisture or ions involved, the aluminum loses.
phillpot said:
No.
If you're loosing sleep over it how about Stainless anti seize... and there's £25 off!
I worked in a nuclear power station and the most common lubricant for stainless steel was basically 'Milk of Magnesia'
If you're loosing sleep over it how about Stainless anti seize... and there's £25 off!
I worked in a nuclear power station and the most common lubricant for stainless steel was basically 'Milk of Magnesia'
Edited by phillpot on Sunday 3rd April 06:42
upperthong said:
Ah, something I know about for once!
Yes, aluminum and stainless steel can and do corrode when put together and the environment that they are in will determine the speed that the reaction occurs. The two differing metals set up a galvanic couple (aka a small battery) and corrode. The aluminum loses.
Add in some moisture and the reaction happens faster.
Add in some other electrolyte or source of ions, like something acidic or basic or salty or etc, and the corrosion reaction will occur even faster.
So, totally dry and totally clean (anodized aluminum and passivated stainless steel) would last for a while.
But if you have any moisture or ions involved, the aluminum loses.
To save me trying to search that deep into my memory banks (getting hard at my age!), I think the practical issues are firstly whether the galvanic reaction between stainless fixings and alloy is greater or less(as I believe) than between steel fixings and alloy and secondly whether the inclusion of copper in the grease used to protect the components has any adverse effect?Yes, aluminum and stainless steel can and do corrode when put together and the environment that they are in will determine the speed that the reaction occurs. The two differing metals set up a galvanic couple (aka a small battery) and corrode. The aluminum loses.
Add in some moisture and the reaction happens faster.
Add in some other electrolyte or source of ions, like something acidic or basic or salty or etc, and the corrosion reaction will occur even faster.
So, totally dry and totally clean (anodized aluminum and passivated stainless steel) would last for a while.
But if you have any moisture or ions involved, the aluminum loses.
What do you think?
The copper grease would help, but I work in stainless and aluminium all day, every day, I have seen many problems with stainless to aluminium contamination to the point where they appear to have welded each-other together. it is a problem despite whatever anyone else on here is saying. I have day to day experience of it. We advise our customers aluminium to aluminium, stainless to stainless. If that can't be avoided, then yes, use a lubricant such as copper to break the reaction. But I would advise to periodically check to see if they are starting to 'bond' or if the aluminium is starting to corrode.
upperthong said:
The copper grease would help, but I work in stainless and aluminium all day, every day, I have seen many problems with stainless to aluminium contamination to the point where they appear to have welded each-other together. it is a problem despite whatever anyone else on here is saying. I have day to day experience of it. We advise our customers aluminium to aluminium, stainless to stainless. If that can't be avoided, then yes, use a lubricant such as copper to break the reaction. But I would advise to periodically check to see if they are starting to 'bond' or if the aluminium is starting to corrode.
On our boat we use Duralac when we have to put say stainless steel fittings into an alloy part such as the mast or a spar.http://www.amazon.co.uk/Duralac-Anti-Corrosive-Joi...
I have no idea whether this would cope with the tempperatures that you'd find in or around an engine though.
glenrobbo said:
Lost count the number of times i`ve used that, or even JC11.As a slight aside, don't do Stainless fixings up with an air tool. The stainless suffers from 'Galling' and it effectively welds itself into the threaded bit, usually long before it clamps up.
We were fitting roof racks onto Defenders and went through a number of broken fixings. The workshop didn't like having to go back to a hand ratchet to tighten them up. We tried lubricants but still couldn't stop the bolts shearing off.
We were fitting roof racks onto Defenders and went through a number of broken fixings. The workshop didn't like having to go back to a hand ratchet to tighten them up. We tried lubricants but still couldn't stop the bolts shearing off.
Thanks everyone; Most of my questions have been answered.
I have also been doing a bit more reading.
Galvanic cell voltages are;-
Stainless Steel & Mild/Carbon Steel = 0.5V
Stainless Steel & Aluminium = 0.58V
Mild Steel & Aluminium = 0.08V
Copper & Aluminium = 0.53V
Copper & Stainless Steel = 0.05V
Copper & Mild Steel = 0.45V
NACE recommend that in brine galvanic voltages should not exceed 0.25V, and in fresh water should not exceed 0.45V.
I was surprised that Stainless steel in Mild steel has a galvanic difference of 0.5V = very corrosive, whereas Mild steel in aluminium is only 0.08V = almost no galvanic corrosion. (Compared with Stainless steel in aluminium = 0.58V.)
I have not been able to find out whether the insulating jointing compounds recommended for dissimilar metals are able to withstand engine temperatures and oils.
But the proof of the pudding is that no one appears to have actually experienced any problems with Stainless and copper grease in Aluminium on our cars. So I shall leave my Stainless bolts in place.
I have also been doing a bit more reading.
Galvanic cell voltages are;-
Stainless Steel & Mild/Carbon Steel = 0.5V
Stainless Steel & Aluminium = 0.58V
Mild Steel & Aluminium = 0.08V
Copper & Aluminium = 0.53V
Copper & Stainless Steel = 0.05V
Copper & Mild Steel = 0.45V
NACE recommend that in brine galvanic voltages should not exceed 0.25V, and in fresh water should not exceed 0.45V.
I was surprised that Stainless steel in Mild steel has a galvanic difference of 0.5V = very corrosive, whereas Mild steel in aluminium is only 0.08V = almost no galvanic corrosion. (Compared with Stainless steel in aluminium = 0.58V.)
I have not been able to find out whether the insulating jointing compounds recommended for dissimilar metals are able to withstand engine temperatures and oils.
But the proof of the pudding is that no one appears to have actually experienced any problems with Stainless and copper grease in Aluminium on our cars. So I shall leave my Stainless bolts in place.
I am amazed that the galvanic voltage for mild steel to aluminium is so much less than stainless to aluminium! Yet in practice the corrosion experienced on say a thermostat housing with steel bolts through an alloy casting is a real problem whereas stainless bolts 'appear' to greatly reduce that problem.
Perhaps the issue isnt primarily galvanic? Getting a headache now trying to remember my materials sciences!
Perhaps the issue isnt primarily galvanic? Getting a headache now trying to remember my materials sciences!
greymrj said:
Perhaps the issue isnt primarily galvanic?
I think the primary process is oxidation, where the iron in the steel reacts with water/air/moisture (all contain oxygen) and is oxidised to iron oxide (i.e. rust). Stainless steel contains enough chromium to form an oxygen blocking chromium oxide layer, which inhibits the further oxidation (rusting) of the iron content of the "stainless steel".
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