RC99
Diamond
- Joined
- Mar 26, 2005
Can anyone tell me if I use zinc plated bolts on a galvanised steel frame will the zinc and galvanising react with one another and cause premature rusting???
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zinc bolts on galvanised steel
- Thread starter RC99
- Start date
- Replies 17
- Views 28,299
LexD
Hot Rolled
- Joined
- Sep 4, 2002
- Location
- Riddells Creek,Victoria,Australia
Ringer, hot dip galvanising is done with molten Zinc, the same metal used to zinc plate your bolts, therefore there will be no adverse reaction between the two.
Forrest Addy
Diamond
- Joined
- Dec 20, 2000
- Location
- Bremerton WA USA
Zinc plated bolts have some corrosion resistance whose durability depends on their environment. If your application justifies galvanized steel construction, perhaps galvanized fasteners should be employed.
plannerpower
Hot Rolled
- Joined
- Jul 20, 2005
- Location
- Newcastle, Australia
There are some pretty dreadful "zinc-plated" bolts out there these days. The hardware-store kind seem to be getting worse and worse; they will virtually dissolve in a year or two under adverse conditions.
As Forrest said, hot-dip galvanised bolts/nuts/washers are a much better proposition.
Find a good "boltatorium" (that's what my local engineering supplies bloke calls the "bolts" section of his shop
) and see what they have.
This may be useful;
http://www.gaa.com.au/design3.pdf
As Forrest said, hot-dip galvanised bolts/nuts/washers are a much better proposition.
Find a good "boltatorium" (that's what my local engineering supplies bloke calls the "bolts" section of his shop
This may be useful;
http://www.gaa.com.au/design3.pdf
RC99
Diamond
- Joined
- Mar 26, 2005
Unfortunately galvanised whitworth(or unified for that matter) bolts are no longer obtainable in Oz..The only galvanised bolts you can get are metric and the manufacturers of the galvanised frame i have purchased has not moved over to metric bolts yet they just use zinc plated in leiu of the galvanised bolts they used to supply...
The main reason I asked is that our roofs on our houses/sheds here are corrugated iron...It is coated with a product called zincalume...It is a zinc, silicon, aluminium coating that is supposed to outlast galvanising....Now if you use this zinculume in conjunction with galvanised guttering the guttering will rust out in a few years from a reaction even though the two items do not touch..
So i just assumed that zinc plated and galvanised might react in some way..
The main reason I asked is that our roofs on our houses/sheds here are corrugated iron...It is coated with a product called zincalume...It is a zinc, silicon, aluminium coating that is supposed to outlast galvanising....Now if you use this zinculume in conjunction with galvanised guttering the guttering will rust out in a few years from a reaction even though the two items do not touch..
So i just assumed that zinc plated and galvanised might react in some way..
LexD
Hot Rolled
- Joined
- Sep 4, 2002
- Location
- Riddells Creek,Victoria,Australia
Ringer, you can get galvanized nuts and bolts in Australia although they are much more expensive than zinc plated. If you are using the plated ones indoors they will be O.K.
Forrest Addy
Diamond
- Joined
- Dec 20, 2000
- Location
- Bremerton WA USA
We often use a "cold galvanize" from a spraycan to coat freshly fastened equipment destined for out of doors. It works well here in cool humid Puget Sound country (about like Tasmania I imagine). Salt water dock hardware, dolphin anchors, navigation marker structure all show where the contractors used this spray and it holds up almost as well as hot dipped galvanize.
The better grades contain 80 by weight elemental zinc with a binder of some kind.
If you can get this spray in Oz, use zinc plated stuff and foof it pretty good with the cold galvanise. It's not pretty but you can paint over it.
The better grades contain 80 by weight elemental zinc with a binder of some kind.
If you can get this spray in Oz, use zinc plated stuff and foof it pretty good with the cold galvanise. It's not pretty but you can paint over it.
RC99
Diamond
- Joined
- Mar 26, 2005
Yes Forrest that is available here and I have a couple of cans of it onhand...
Luthor I have asked around various bolt suppliers and they all tell me galvanised whitworth bolts are now made of unobtanium...
Thanks for the help everyone....I might just give the bolts a spray with coldgal after I erect this tower...
Luthor I have asked around various bolt suppliers and they all tell me galvanised whitworth bolts are now made of unobtanium...
Thanks for the help everyone....I might just give the bolts a spray with coldgal after I erect this tower...
mikerr
Aluminum
- Joined
- Mar 5, 2005
- Location
- Sydney Australia
Ringer, I just have to ask. What is going on the tower? Water,Diesel, Windmill, Gun Turret, Bat Cannon....
Nothing to do with your question just curious.
Rgds
Michael
Nothing to do with your question just curious.
Rgds
Michael
Alan
Cast Iron
- Joined
- Nov 28, 2002
- Location
- Perth, Australia
Ringer,
Do a google on "galvanic series chart" it should provide some comparative info.
Do a google on "galvanic series chart" it should provide some comparative info.
RC99
Diamond
- Joined
- Mar 26, 2005
mikerr a windmill is going on the tower..
Thanks for that Alan, I will look into it a bit more..
Thanks for that Alan, I will look into it a bit more..
LexD
Hot Rolled
- Joined
- Sep 4, 2002
- Location
- Riddells Creek,Victoria,Australia
Ringer, you really need to try a few more suppliers if you want to use gal bolts. I can name at least 6 places within 4km. of me that stock them, even Bunnings.
Forrest and Ringer:
How do you keep those cold galvanizing paint cans from clogging? Even the most careful shaking before, and clearing after use seems to be dicey as far as keeping the can sprayable. (of course it is Rustoleum brand.... that might be part of it)
Concur that it works well... I have some stuff on a roof (Solar array) that has been up many years and the cold galvanizing is still good on the parts.
How do you keep those cold galvanizing paint cans from clogging? Even the most careful shaking before, and clearing after use seems to be dicey as far as keeping the can sprayable. (of course it is Rustoleum brand.... that might be part of it)
Concur that it works well... I have some stuff on a roof (Solar array) that has been up many years and the cold galvanizing is still good on the parts.
Sea Farmer
Diamond
- Joined
- Mar 25, 2006
- Location
- Cape Cod, Massachusetts
My experiences with a few tons of steel in tbhe ocean on an aquaculture operation:
Hot-dip galvanized fasteners last longer than zinc-plated.
Zinc-plated fasteners seem to vary in quality, but I can't assess that visually, standing in the store looking at them, or from a catalogue description.
Some China-made anchor shackles that are supposedly hot-dip galvanized rust in less than one year, while American-made galvanized shackles in service next to them have been rustfree for four years. Never saw any Australian shackles
I use a lot of cold spray galvanize and it works well, better than zinc plated fasteners. But I just checked two cans on the shelf; Rustoleum brand is 93% zinc, CRC is 95%. The 93% is ok for touching up scratches on a hot galvanized piece but 95% is more effective for treating unfinished steel.
Cold galvy paint seems to be a fairly soft finish, or I'm applying it wrong, so if a part is subject to abrasion I paint over the galvy spray with an autobody undercoat type product, or even truck bed liner paint.
Local welding supply sells cans of brush-on cold galvy paint. Cans are very heavy for their size, lots of metal in there. Haven't tried it, don't know the name or specs. Anyone have any experience with this stuff?
Hot-dip galvanized fasteners last longer than zinc-plated.
Zinc-plated fasteners seem to vary in quality, but I can't assess that visually, standing in the store looking at them, or from a catalogue description.
Some China-made anchor shackles that are supposedly hot-dip galvanized rust in less than one year, while American-made galvanized shackles in service next to them have been rustfree for four years. Never saw any Australian shackles
I use a lot of cold spray galvanize and it works well, better than zinc plated fasteners. But I just checked two cans on the shelf; Rustoleum brand is 93% zinc, CRC is 95%. The 93% is ok for touching up scratches on a hot galvanized piece but 95% is more effective for treating unfinished steel.
Cold galvy paint seems to be a fairly soft finish, or I'm applying it wrong, so if a part is subject to abrasion I paint over the galvy spray with an autobody undercoat type product, or even truck bed liner paint.
Local welding supply sells cans of brush-on cold galvy paint. Cans are very heavy for their size, lots of metal in there. Haven't tried it, don't know the name or specs. Anyone have any experience with this stuff?
franco
Hot Rolled
- Joined
- Jul 8, 2003
- Location
- Cairns, Queensland, Australia
Sea Farmer,
About 20 years ago I made a boat trailer drawbar extension from hot rolled steel, and painted it with a couple of heavy coats of a brush-on cold galvanising paint; also painted a weld on a clamp nut on the back of the trailer, which was submerged each time the boat was launched or retrieved. The trailer was used frequently for about ten years in a salt water environment and washed down with fresh water after each use. Since then it has not been subjected to use in salt water, but is still in limited use for another purpose.
Neither the weld at the back of the trailer nor the drawbar extension is showing any sign of rusting. To satisfy my curiosity I unbolted the extension from the trailer recently to check the contact area between the extension and the original galvanising on the trailer. There was no sign of rusting or electrolytic action at the interface between the extension and the original trailer frame.
It appears to me that this particular (Australian made) zinc rich paint is as durable as the original hot dip galvanising.
franco.
About 20 years ago I made a boat trailer drawbar extension from hot rolled steel, and painted it with a couple of heavy coats of a brush-on cold galvanising paint; also painted a weld on a clamp nut on the back of the trailer, which was submerged each time the boat was launched or retrieved. The trailer was used frequently for about ten years in a salt water environment and washed down with fresh water after each use. Since then it has not been subjected to use in salt water, but is still in limited use for another purpose.
Neither the weld at the back of the trailer nor the drawbar extension is showing any sign of rusting. To satisfy my curiosity I unbolted the extension from the trailer recently to check the contact area between the extension and the original galvanising on the trailer. There was no sign of rusting or electrolytic action at the interface between the extension and the original trailer frame.
It appears to me that this particular (Australian made) zinc rich paint is as durable as the original hot dip galvanising.
franco.
Peter S
Diamond
- Joined
- May 6, 2002
- Location
- Auckland, New Zealand
Good grief, Sea Farmer, zinc plated (ie electroplated zinc) fasteners are intended for indoors, dry applications. Just a joke outside, never mind near the sea. I suppose you can find them on vehicles, but where exposed to the weather, unless painted, the zinc will soon be gone.
Hot dip galv is hugely different, and intended for outdoors.
316 stainless is normal on salt-washed fasteners.
One of the problems, in my little experience, with the cold galv seems to be it is not as tough, ie will wear off, scratch easily etc. Looks not so good either.
Hot dip galv is hugely different, and intended for outdoors.
316 stainless is normal on salt-washed fasteners.
One of the problems, in my little experience, with the cold galv seems to be it is not as tough, ie will wear off, scratch easily etc. Looks not so good either.
Sea Farmer
Diamond
- Joined
- Mar 25, 2006
- Location
- Cape Cod, Massachusetts
franco, agree completely a washdown after saltwater use makes a huge diference in longevity. I thought the brush-on product would be more durable than the spraycan variety, it typically is better in regular paint. thanks for the report.
Peter S, yeah I know, sometimes in a jam I just go to the big box store and buy what's on the shelf to get the job done. The tide waits for no man. Also agree with the lack of toughness of the cold galvy, the truck bed liner paint is the better-than-nothing patch. The reason we go for quick fixes here is that our weather usually destroys metal before corrosion can.
Hereabouts the bays and harbors freeze about 5 years out of ten, ice can get a few feet thick (2003 it was sixteen feet thick) and scours the farms with every tide for a few weeks. We pull the oysters out of the ocean and put them into cold storage to keep them from getting crushed, but no one has the capacity to pull all their metal structures out as well. And the ice mangles it. Viciously. Absent that we'd make everything out of 316 stainless or marine-grade aluminum. Instead we make it out of hot-rolled, and make new stuff when the old stuff gets crushed. Few things survive enough winters to die of corrosion.
A lot of my aquaculture gear comes from Australia (none from New Zealand, sorry Peter), some pretty creative minds in the oyster business there.
Peter S, yeah I know, sometimes in a jam I just go to the big box store and buy what's on the shelf to get the job done. The tide waits for no man. Also agree with the lack of toughness of the cold galvy, the truck bed liner paint is the better-than-nothing patch. The reason we go for quick fixes here is that our weather usually destroys metal before corrosion can.
Hereabouts the bays and harbors freeze about 5 years out of ten, ice can get a few feet thick (2003 it was sixteen feet thick) and scours the farms with every tide for a few weeks. We pull the oysters out of the ocean and put them into cold storage to keep them from getting crushed, but no one has the capacity to pull all their metal structures out as well. And the ice mangles it. Viciously. Absent that we'd make everything out of 316 stainless or marine-grade aluminum. Instead we make it out of hot-rolled, and make new stuff when the old stuff gets crushed. Few things survive enough winters to die of corrosion.
A lot of my aquaculture gear comes from Australia (none from New Zealand, sorry Peter), some pretty creative minds in the oyster business there.
RC99
Diamond
- Joined
- Mar 26, 2005
OK I will go over the zinc plated bolts with some high % zinc spray(I'll make sure to get top quality Aussie made stuff not that cheap imported US stuff made using cheap mexican labour 
It appears according to the galvonic chart that hot dipped and electroplated zinc won't react with each other....The bolts have not arrived yet, it appears the person who packed the tower bundle up at the factory thought bolts were not needed in assembly...
It appears according to the galvonic chart that hot dipped and electroplated zinc won't react with each other....The bolts have not arrived yet, it appears the person who packed the tower bundle up at the factory thought bolts were not needed in assembly...
