Les Henson Posted December 12, 2007 Share Posted December 12, 2007 Is it better or worse to use a stainless bolt in alloy, rather than BZP? Also - would a stainless nut or bolt used in place of a steel one have the same tensile strength for any given torque figure? Les. Quote Link to comment Share on other sites More sharing options...
T1G UP Posted December 12, 2007 Share Posted December 12, 2007 Stainles Nuts and bolts are ,IMO, onlt to be used where they REALLY need to be used,ie in the correct enviroment. I'd much rather use BZP's on landy's etc as the s/s variety have a tendancy to "pick up" binding the thread and having to be cut off. Thy also don't like to much damage and on a landy you get damage! BZP for me! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted December 12, 2007 Share Posted December 12, 2007 ISTR stainless is not equal to steel, either through being more brittle or such like (I'm sure a metallurgist will be along in a minute). Also it's further from Ali in the galvanic corrosion stakes so may accelerate corrosion. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted December 12, 2007 Share Posted December 12, 2007 I read somewhere that the S/S hinge bolt kits sold by various suppliers are great except that they make the panels corrode instead of the bolts so not really progress in that respect Quote Link to comment Share on other sites More sharing options...
English Gent Posted December 13, 2007 Share Posted December 13, 2007 I used a large number of stainless fixings on my IIA during the various rebuilds, and I have always found that I get a small white powder residue at the panel joint which I would say will be aluminium oxide formed as a corrosion product. However, the SS nut and bolts always come undone so I'm not fighting rusty steel. I wouln'd say I've suffered 'massive' corrosion with bolts falling through the panels, but perhaps I'm lucky. If you want to protect against galvanic corrosion, then the simplest way is to provide a layer of inhibitor to stop the flow of electrons between the anode and cathode of the glavanic cell (Flippin heck, these cogs in my head haven't turned for a while) and the simplest method is a dollop of coppergrease on the bolts prior to installation and another dollop over the end of the thread. Buy coppergrease in the tin rather than a tube and just use a paint brush. Stainless steel bolts will fail at a lower torque value than standard high tensile steel and as such any load dependent bolt and nut should be HT but with a nice layer of coppergrease, although the application of coppergrease will alter the amount of torque required over a dry fitting, not htat I've had too many things fall apart so far.... touch wood. Quote Link to comment Share on other sites More sharing options...
disco tony Posted December 13, 2007 Share Posted December 13, 2007 "provide a layer of inhibitor to stop the flow of electrons between the anode and cathode ..........the simplest method is a dollop of coppergrease on the bolts" Isn't copper one of the best conductors of electricity? Quote Link to comment Share on other sites More sharing options...
English Gent Posted December 13, 2007 Share Posted December 13, 2007 "provide a layer of inhibitor to stop the flow of electrons between the anode and cathode ..........the simplest method is a dollop of coppergrease on the bolts"Isn't copper one of the best conductors of electricity? Ah, yes, well I did say the cogs haven't turned for a while... however, its fine particles of copper embedded in a nice grease. I wonder what would happed if I stuck a continuity meter in a tub of the stuff? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted December 13, 2007 Share Posted December 13, 2007 I'd use ordinary grease, cheaper than Coppaslip. Or you could use the proper stuff - Duralac Quote Link to comment Share on other sites More sharing options...
disco tony Posted December 13, 2007 Share Posted December 13, 2007 Or a cheap petroleum jelly, (vaseline type stuff)? Quote Link to comment Share on other sites More sharing options...
Les Henson Posted December 13, 2007 Author Share Posted December 13, 2007 Not a lot of good if you have to use threadlocking compound though, unless it does the same thing. Les. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted December 14, 2007 Share Posted December 14, 2007 I'm guessing a threadlock like loctitte is non conductive, but you never know. If you're working with things like body panels, that are painted, the paint will do the isolating quite nicely. normally the rust from steel cracks the paint, which lets the water in around the fitting etc. It's worth noting that stainless and aluminium are used together all over boats, which exist in a moist sea(salt) water environment, and they do ok. Quote Link to comment Share on other sites More sharing options...
Betsy Posted December 14, 2007 Share Posted December 14, 2007 Going back to my aircraft engineering days (loooooong time ago). Where we were using SS fittings on the alloy structure, they were always isolated by use of a substance that I cannot remember the name of, but it was know amongst the engineers as "Yellow Sh*t" !!! It was a thick yellow paste that was liberally applied to the joint faces of the fixing or fitting, and to the threads on a bolt or nut. After the fitting or fixing was attached, then it was over painted on all joint faces with a rubberised version of "Yellow Sh*t" This left the item isolated and sealed. It was not very common to find corroded or seized bolts on the aircraft I worked on. These included Nimrods, which operate at low levels over the sea, and got plenty of salty water to help things corrode. This procedure applied to all steel fittings though. Even rivets had an overpaint of sealer before the paint was applied. Quote Link to comment Share on other sites More sharing options...
Lars L Posted December 14, 2007 Share Posted December 14, 2007 This is the web page of a Swedish company selling something similar: http://www.townshend.se/tefgel/tefgel.asp?ModuleItemID=121 Maybe a search will find a dealer a bit closer. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted December 14, 2007 Share Posted December 14, 2007 Threadlock may be non-conductive but it doesn't insulate the fastener, just stops it coming loose. The answer to the original question is: SS will corrode the ali, SS bolts do not have the same tensile strength as steel. Just use BZP and don't leave it for the next 30 years to form into a small lump of rust. Quote Link to comment Share on other sites More sharing options...
Betsy Posted December 14, 2007 Share Posted December 14, 2007 I think the most important thing is to stop conductivity as best as possible, then seal the joint to prevent oxygen, and moisture getting in. Moisture increases conductivity, oxygen is the catalyst for corrosion. If nothing else is available, then a good coat of paint would probably to the trick. Quote Link to comment Share on other sites More sharing options...
Raggylad Posted December 14, 2007 Share Posted December 14, 2007 I think the most important thing is to stop conductivity as best as possible, then seal the joint to prevent oxygen, and moisture getting in. Moisture increases conductivity, oxygen is the catalyst for corrosion. If nothing else is available, then a good coat of paint would probably to the trick. Quite correct for non-stainless steels, but incorrect for stainless. If you isolate stainless from the air, you eventually get what is known in the marine engineering world as crevice corrosion; it tends to form in the threads of bolts, the corners of deck fittings and suchlike confined spaces. A classic is the turnbuckles for yacht mast standing rigging, which people tend to cover to prevent ropes snagging and also the stainless wire rigging itself which corrodes deep in the strands & fails with no visible warning of decay - expensive ! The best way to avoid crevice corrosion in stainless is to leave it exposed to the air; the stainless properties are in the oxidised outer surface of the steel - which needs oxygen to maintain its integrity in areas exposed to potentially corrosive forces. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted December 14, 2007 Share Posted December 14, 2007 I have always used top hat neoprene washers to isolate SS fixings. Probably less messy than yellow Sh!t!! but don't know if they are as effective... Quote Link to comment Share on other sites More sharing options...
nickm Posted December 14, 2007 Share Posted December 14, 2007 so after all that would I be best to use bzp bolt as a drain plug on an 8274 casing ? or a standard bolt and cover it in yellow gunk Quote Link to comment Share on other sites More sharing options...
Ozyboy Posted December 14, 2007 Share Posted December 14, 2007 I have always used top hat neoprene washers to isolate SS fixings. Probably less messy than yellow gunk but don't know if they are as effective... Interesting thread.... (Get'it Thread)...... Different approach's make interesting reading.... Ditto last remarks. I use a stroke of a waxoil soak'd brush on the thread for lubrication, and a piece of neoprene rubber when against chassis etc No adverse corrosion on the 90 i built 5 years ago.... Bigger corrosion issue comes from steel (I believe), LR appear to fit body cappings etc etc, and then send bodywork to the spray shop etc thus, nil paint on the aly against the steel... And we all wonder why the darn things fall apart in 5 years. Quote Link to comment Share on other sites More sharing options...
gazelle Posted December 14, 2007 Share Posted December 14, 2007 It's worth noting that stainless and aluminium are used together all over boats, which exist in a moist sea(salt) water environment, and they do ok. In salt water it is even more of a problem. Stainless stantions get corroded to ali station bases, steel hulls, aluminium propellers and brackets get eaten by galvanic corrosion. Underwater protection is provided by sacrificial anodes made of Zinc in salt water and magnesium in fresh. More are used on vessels with more steel. So yes combinations of steel and aluminium are used in a marine environment, but the protection is there - and usually out of sight. The zinc anode is the pear shaped thing behind the propeller. The LR content is in the background. I would agree that the only way to reduce the galvanic corrosion is to isolate the two pieces, as discussed earlier Quote Link to comment Share on other sites More sharing options...
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