aluminium and steel trailer corrosion questions

Post by **ctguru** » Thu Mar 20, 2008 10:10 am

can i use aluminium plate for the sides of a painted steel framed trailer without causing any corrosion problems?

Post by **bazzle** » Thu Mar 20, 2008 11:05 am

Glue them on with sikaflex.

ABzzle

Post by **date** » Thu Mar 20, 2008 1:38 pm

You can use aluminium against steel, but it MUST be electrically insulated from the steel, or corrosion will occur. This includes fixing the panels eg steel screws - hence the comment above about glueing the panels. If you still want to use screws, you must isolate them from the aluminium by plastic or rubber grommets. Any contact between the two metals, and corrosion of one of them will ensue. A good coat of paint will be sufficient to insulate the steel.

Post by **chikoroll_** » Thu Mar 20, 2008 6:14 pm

wow.
first time i heard of this....

why would either corrode?

Post by **ctguru** » Thu Mar 20, 2008 6:49 pm

date wrote:You can use aluminium against steel, but it MUST be electrically insulated from the steel, or corrosion will occur.

I assume then even if I use stainless pop rivets, the metals will not be electrically insulated and there would be corrosion.

cheers

Post by **date** » Thu Mar 20, 2008 7:53 pm

For corrosion to occur, you need two things to happen:
1 You need oxygen (including dissolved oxygen in water)
2 An electrical current - you need an electrolyte and a potential (voltage) difference to drive the current.

The electrical current comes from the natural potentials of the metals. There is a chart called the Galvanic series, giving the potentials of each type of metal. Gold is at one end, and aluminium is at the other. Carbon steels are low down and close to Aluminium. Stainless steels are way up the scale. Dry cell batteries use the natural potential differences to generate voltages.

In order to prevent corrosion, you need to stop the current flow. Hence you paint steel, or insert an insulating barrier between the dissimilar metals. Or ensure that the joints are dry - this means no electrolyte and hence no current. For example, if you drop a stainless steel washer in the bottom of an aluminium boat, it will sit there in the bilge and burn a hole right through the skin of the hull.

This is a simplified version of corrosion mechanisms, but hopefully will gove you an idea of what goes on. If yoy can keep it all totally dry (hence no electrolyte for the current to flow), or keep the parts electrically isolated (painting, rubber or even a good coating of glue) you should have no problems.

Hope this helps

Post by **toughnut** » Thu Mar 20, 2008 7:53 pm

The difference in metals create electrolisis (spelling) if they are touching each other. You can still do this and not have any problems if you use a couple of anodes that are normally used on boats. These will corode quicker than the rest of the metal that they are attached to. You'll have to replace them every couple of years depending on their size and how fast they corrode.

Post by **chikoroll_** » Thu Mar 20, 2008 9:07 pm

so basicly the crappy ones like aluminium are having the atoms sucked out of them by the other metals?

Post by **-Scott-** » Thu Mar 20, 2008 9:29 pm

chikoroll_ wrote:so basicly the crappy ones like aluminium are having the atoms sucked out of them by the other metals?

Electrons. Aluminium atoms are, by definition, aluminium. The metal doesn't migrate, only the electrons.

Post by **chikoroll_** » Thu Mar 20, 2008 10:41 pm

....i think i'll go back to playing with my wood

Post by **toughnut** » Thu Mar 20, 2008 10:50 pm

chikoroll_ wrote:....i think i'll go back to playing with my wood

It's not as bad as it sounds. I used alloy checker plate riveted straight to my steel tray on my patrol and had no problems over two years. You just need to be aware that the metal is different and corrosion will occur quicker if they are in contact. Just maintain it and keep it clean or even spray it with an anti corrosion occasionally.

Post by **-Scott-** » Thu Mar 20, 2008 11:07 pm

Or rivet it together and give it a good coat of paint.

Post by **zagan** » Fri Mar 21, 2008 2:22 am

chikoroll_ wrote:so basicly the crappy ones like aluminium are having the atoms sucked out of them by the other metals?

Metal loses it's + electrons.

If you use an electronic rust stopper, it simply adds or replaces the + electrons in the metal. If you add enough electrons you have no rusting or very little rusting.

I took a look for info on this myself, as I didn't think it was quite right, as it seems that people are saying, the aluminium will rust out real quick, but I don't think that will happen, by quick I mean in a few months or 1-2 years.

Galvanic Corrosion, is based on metal/s rusting in sea water, not on dry land.

Overall though, are you going to be chucking 3 to 5mm sheets on this trailer? because aluminium is a soft metal.

Post by **V8Patrol** » Fri Mar 21, 2008 7:27 am

Rule of thumb........

A weaker metal will corrode first when placed against a differant metal.

This applies to all metals when placed against either a stronger or weaker metal and cunductivity is allowed to proceed.....
alloy corrodes to mild steel,
mild steel corrodes to stainless steel
etc etc

I had an ex-army trailer which was an alloy tub placed on a mild steel frame, the steel frame has a std coat of paint ( army green ) applied to it as does the alloy tub.....

The mounting of the tub to the 'chassis' is via 8 alloy lugs welded to the tub that are 10mm thick and 60mm wide by 100mm long.
These 'tags' are the only contact points between alloy and steel.

The tub has never been removed and there are no signs of corrosion, the trailer would be 30 years old and was stored out in the elements 24/7 when I owned it, the same applies to its current owner's storage place...... under a tree !

Post by **macca81** » Fri Mar 21, 2008 8:00 am

so, asides from glue, what do ya use to join them together? obviously a traditional nut n bolt wont work.....

Post by **chunderlicious** » Fri Mar 21, 2008 8:18 am

heres the one i use for roofing. a galvanised steel roof will burn a hole straight throught a zincalume coated steel gutter as the zincalum will sacrifice itselfto "protect" the parent metal. it will then keep these electrons flowing with the water and if you use a steel screw down the gutter or downpipe it will increase in size over a few years and you wont be able to get it out.

oh and the zincalume corrodes and holes after only 5 or 6 years so if youve got an old house with veejay boards inside then get your gutter replaced when they do a reroof.

GALVANIC SCALE
ANODIC / LESS NOBLE / CORRODED END
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Stainless Steel, Types 304 and 316 (active)*
Lead-Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel, Types 304 and 316 (Passive)
CATHODIC / MORE NOBLE / PROTECTED END
*Active Stainless Steel is stainless steel that hasn’t been chemically cleaned.

Post by **chunderlicious** » Fri Mar 21, 2008 8:22 am

the full list

Graphite
Palladium
Platinum
Gold
Silver
Titanium
Stainless steel (316 passive)
Stainless Steel (304 passive)
Silicon bronze
Stainless Steel (316 active)
Monel 400
Phosphor bronze
Admiralty brass
Cupronickel
Molybdenum
Red brass
Brass plating
Yellow brass
Naval brass 464
Uranium 8% Mo
Niobium 1% Zr
Tungsten
Stainless Steel (304 active)
Tantalum
Chromium plating
Nickel (passive)
Copper
Nickel (active)
Cast iron
Steel
Lead
Tin (pretty much gal steel)
Indium
Aluminum
Uranium (pure)
Cadmium
Beryllium
Zinc plating (zincalume)
Magnesium

Post by **Strange Rover** » Fri Mar 21, 2008 8:26 am

Damn!!!! If you read all this then Im amazed that anything thats made of aluminium and steel would be able to exist in our world.

Think of all the things made from aluminium and are bolted to steel...I used to have a 1974 Range Rover - aluminium panels bolted to steel framework. They must have really sorted out there electrical insulation cause that thing was 30 years old and still in one piece.

What about aluminium hand rails in steel buildings - how do they manage to not corrode and disappear before our eyes.

What about all the steel chassis trailers with aluminium tops that have been built by lots of different manufacturers - these things easily outlast a totally steel trailer especially if you treat them badly and leave wet soil and crap in them.

I think most real world experience shows that you will be fine using aluminium plate for the sides of a painted steel framed trailer without causing any corrosion problems - no matter how you attach them. If you were going to use the trailer as a boat and float around in it in the ocean then I would probably want to get rig of the steel.

Sam

Post by **Strange Rover** » Fri Mar 21, 2008 8:30 am

Ive even got a better - just bought a 1950 Series 1 Landrover - aluminium panels bolted to steel frame...this thing is almost 60 years old and still in one piece.

Sam

Post by **Strange Rover** » Fri Mar 21, 2008 8:31 am

chunderlicious wrote:heres the one i use for roofing. a galvanised steel roof will burn a hole straight throught a zincalume coated steel gutter as the zincalum will sacrifice itselfto "protect" the parent metal. it will then keep these electrons flowing with the water and if you use a steel screw down the gutter or downpipe it will increase in size over a few years and you wont be able to get it out.

oh and the zincalume corrodes and holes after only 5 or 6 years so if youve got an old house with veejay boards inside then get your gutter replaced when they do a reroof.

GALVANIC SCALE
ANODIC / LESS NOBLE / CORRODED END
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Stainless Steel, Types 304 and 316 (active)*
Lead-Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel, Types 304 and 316 (Passive)
CATHODIC / MORE NOBLE / PROTECTED END
*Active Stainless Steel is stainless steel that hasn’t been chemically cleaned.

So your saying that in the case of the aluminium panels on the steel framed Landrover that the aluminium should corrode before the steel???

Sam

Post by **toughnut** » Fri Mar 21, 2008 9:21 am

If they are touching each other. Which of course they wouldn't be because the 60 yo ruber body mounts would be in great condition.

Post by **nastytroll** » Fri Mar 21, 2008 9:22 am

Strange Rover wrote:
chunderlicious wrote:heres the one i use for roofing. a galvanised steel roof will burn a hole straight throught a zincalume coated steel gutter as the zincalum will sacrifice itselfto "protect" the parent metal. it will then keep these electrons flowing with the water and if you use a steel screw down the gutter or downpipe it will increase in size over a few years and you wont be able to get it out.

oh and the zincalume corrodes and holes after only 5 or 6 years so if youve got an old house with veejay boards inside then get your gutter replaced when they do a reroof.

GALVANIC SCALE
ANODIC / LESS NOBLE / CORRODED END
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Stainless Steel, Types 304 and 316 (active)*
Lead-Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel, Types 304 and 316 (Passive)
CATHODIC / MORE NOBLE / PROTECTED END
*Active Stainless Steel is stainless steel that hasn’t been chemically cleaned.
So your saying that in the case of the aluminium panels on the steel framed Landrover that the aluminium should corrode before the steel???

Sam

I was witing for one of the rover boys to pipe up, the ting most people have missed it the electrolite (could be a different name?). eg a lead acid battery is nothing with out the acid to carry the electrons.

Sam if you were to park the rover in salt water, if the ally was unprotected it would corrode rapidly. The salt water would be the electrolite.

Some one feel free to correct me as this is from memory on the unimportant stuff in my head.

If you were to place steel n ally together in a clorine base sanitiser you can fisically see the ally boiling off.

Post by **RUFF** » Fri Mar 21, 2008 10:10 am

toughnut wrote:If they are touching each other. Which of course they wouldn't be because the 60 yo ruber body mounts would be in great condition.

There are aluminium panels also rivited or bolted to steel frames. Not just the body to the chassie.

Post by **chunderlicious** » Fri Mar 21, 2008 10:56 am

nastytroll wrote:
Strange Rover wrote:
chunderlicious wrote:heres the one i use for roofing. a galvanised steel roof will burn a hole straight throught a zincalume coated steel gutter as the zincalum will sacrifice itselfto "protect" the parent metal. it will then keep these electrons flowing with the water and if you use a steel screw down the gutter or downpipe it will increase in size over a few years and you wont be able to get it out.

oh and the zincalume corrodes and holes after only 5 or 6 years so if youve got an old house with veejay boards inside then get your gutter replaced when they do a reroof.

GALVANIC SCALE
ANODIC / LESS NOBLE / CORRODED END
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Stainless Steel, Types 304 and 316 (active)*
Lead-Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel, Types 304 and 316 (Passive)
CATHODIC / MORE NOBLE / PROTECTED END
*Active Stainless Steel is stainless steel that hasn’t been chemically cleaned.
So your saying that in the case of the aluminium panels on the steel framed Landrover that the aluminium should corrode before the steel???

Sam
I was witing for one of the rover boys to pipe up, the ting most people have missed it the electrolite (could be a different name?). eg a lead acid battery is nothing with out the acid to carry the electrons.

Sam if you were to park the rover in salt water, if the ally was unprotected it would corrode rapidly. The salt water would be the electrolite.

Some one feel free to correct me as this is from memory on the unimportant stuff in my head.

If you were to place steel n ally together in a clorine base sanitiser you can fisically see the ally boiling off.

if you connect DC aluminium and steel in mineralised water, the aluminium will transfer over to the steel (plating) same as copper. chlorine may do the same

for the reaction to take place you really need a constant contact of stuff like rain water or salt water etc. for the reaction to keep going. the key thing is it has to be mineralised or impure for the reaction to occur as it wont happen with demineralised water.

Post by **toughnut** » Fri Mar 21, 2008 2:21 pm

RUFF wrote:
toughnut wrote:If they are touching each other. Which of course they wouldn't be because the 60 yo ruber body mounts would be in great condition.
There are aluminium panels also rivited or bolted to steel frames. Not just the body to the chassie.

Hairy Muff. (fair enough)

Post by **Strange Rover** » Fri Mar 21, 2008 3:48 pm

Which is why I said...

If you were going to use the trailer as a boat and float around in it in the ocean

And everybody here definitely isnt....

So everybody saying that you carnt attach aluminium to steel because of electrolysis is absolute rubbish.

I will guarantee that any trailer or 4wd or car that had aluminium attached to steel - the steel will rust first just the same as if it was totally made out of steel - just as it does in any range rover or any landrover.

If your not in the ocean none of the electrolysis matters.

Sam

Post by **Strange Rover** » Fri Mar 21, 2008 3:50 pm

nastytroll wrote:I was witing for one of the rover boys to pipe up, the ting most people have missed it the electrolite (could be a different name?). eg a lead acid battery is nothing with out the acid to carry the electrons.

Sam if you were to park the rover in salt water, if the ally was unprotected it would corrode rapidly. The salt water would be the electrolite.

Some one feel free to correct me as this is from memory on the unimportant stuff in my head.

If you were to place steel n ally together in a clorine base sanitiser you can fisically see the ally boiling off.

The thing you have really missed is that there is no electrolite

Sam

Post by **nastytroll** » Fri Mar 21, 2008 7:11 pm

die electric is what I was thinkin of, not electrolite.
But as you already had known the answer Why not answer for every one else?

And unprotected ally will corrode faster then steel.

Post by **Strange Rover** » Fri Mar 21, 2008 7:24 pm

nastytroll wrote:die electric is what I was thinkin of, not electrolite.
But as you already had known the answer Why not answer for every one else?

And unprotected ally will corrode faster then steel.

I have no idea what die electric is???

Unprotected aluminium will oxidise faster that steel, but then the aluminium oxide actually creates the protective layer and prevents any further oxidisation (or corrosion) - as opposed to steel, the iron oxide doesent protect the steel underneath and therefore keeps rusting. If the aluminium oxide is continuously disturbed then it is possible the aluminium will corrode faster than steel.

But anyway...attaching aluminium panels to a steel trailer is a perfectly normal thing to do.

Sam

Post by **nastytroll** » Fri Mar 21, 2008 8:03 pm

your dead right sam, and people try get too technical with stuff on here. as long as your not building a boat or something in a wet/chemical invironment ally n steel are fine.

look at pan techs, rovers, ally bullbars, some fridges, hydrolics, motorbikes, lawn mowers ect the list is endless.

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aluminium and steel trailer corrosion questions

aluminium and steel trailer corrosion questions

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