Can someone explain this?
 

I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct electrical
contact on the boat will break down the weakest point of the aluminum and cause
holes in the boat. This is especially important if you are a SAL****ER Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or material."

How could you avoid this? The motor is bolted directly to the metal transom
and is grounded, there is contact there. I checked my aluminum boat with a VOM
and there is definately continuity between the boat and the motor. Whats the
difference in letting the motor ground to the boat and not the wiring? What am
I missing here?

Can someone explain this?
 

"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the aluminum and
cause
holes in the boat. This is especially important if you are a SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat with
a VOM
and there is definately continuity between the boat and the motor. Whats
the
difference in letting the motor ground to the boat and not the wiring?
What am
I missing here?



The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.

Can someone explain this?
 

"Calif Bill" wrote in message
ink.net...

The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.



If cars and fancy car audio are any indication, this method (fat wire to
terminal block or battery) may also help reduce ignition noise on the radio.

Can someone explain this?
 

The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.

OK. I can get a ground anywhere too.
So are you saying that if everything is grounded seperately by a wire running
back to the battery it will flow through the wire and not the boat? Mine is
wired this way, but a lot of the electrical devices are mounted directly to the
aluminum and will work without the ground wire.

Is this because the wire has less resistance than the boat?

Is the object here to keep the current at a minimum, Im sure SOME of it will
always go through the hull just because of the motor and the electrical items
attached to the boat.

Is there anyway to test how much is going through the hull and what is
considered a safe level?

Can someone explain this?
 

Well CC, what you are missing is an understanding of electrolysis.
Electrolysis is caused by dis-similar metals in contact with each other,
and
in the presence of a catalyst. (salt) It makes a sort of crude battery,
producing tiny amounts of electricity.

The electricity is made from stripping electrons from the "weakest" of
the
two metals. In this case, the aluminum of your hull. acting as an anode
to
the strongest metal (useually stainelss steel) acting as a cathode. This
has
the apparent effect of burning holes in the metal at the points of
highest
activity. Bronze items are electricaly neutral.

Electrolysis, otherwise known as galvanic corrosion, is especially bad
for
aluminum hulls, and will "burn" holes through the metal. Once burned
through, the hull is near useless, and, in general, cannot be safely
repaired. There are a couple of things you can do to minimize the effect
of
G.C.

1. Paint the hull with a good grade of zinc based primer, covered with
a
top coat of quality marine grade metal paint. This will isolate the
sal****er (catalyst) from the aluminum, and retard corrosion.

2. Install zinc (or magnesium for freshwater) anodes on both the motor
and
the hull. The anodes are sacrificial, and will decay in the presence of
galvanic current. They must be replaced annually or whenever they become
"crusty". DO NOT wait until the zincs are partially dissolved, as they
lose
their protective ability rapidly after the white "crust" forms. If you
are
the thrifty sort, save your old zincs for re-melting.

3. Bond the motor, hull and battery (-) side. Run a bonding strap or
wire
from the negative terminal of the battery to: motor block; motor mount,
hull, control panel, and any dissimilar metal on the hull. I.E.
stainless
steel Cleats, deck fittings, light fixtures, radios, stereos, or any
dis-similar metal where it contacts the hull. This will equalize any
stray
current in the boat and avoid "hot spots" where G.C. does its worst
work.

Zamack or chrome plated zinc cleats and fittings will deteriorate in
salt
water. If your boat is equipped with these fittings from the factory,
replace them.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum
boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the
aluminum
and cause
holes in the boat. This is especially important if you are a
SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat
with a VOM
and there is definately continuity between the boat and the motor.
Whats the
difference in letting the motor ground to the boat and not the
wiring?
What am
I missing here?

Can someone explain this?
 

The wire, being copper, has a much greater potential for carrying current
due to its electron shell. Electricity will always flow along the path of
least resistance. Bonding your boat with copper wire will reduce the points
of oppertunity for electrical conduction through the hull. It will also
equalize stray current electrolysis, and lessen damage to your hull. It is
especially important to make sure tramsmitters and antenna are properly
bonded.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
The amount of current the boat hull carries. I can get a ground from
the
hull, but I run a large wire to a terminal block with ground and power.

OK. I can get a ground anywhere too.
So are you saying that if everything is grounded seperately by a wire
running
back to the battery it will flow through the wire and not the boat? Mine
is
wired this way, but a lot of the electrical devices are mounted directly
to the
aluminum and will work without the ground wire.

Is this because the wire has less resistance than the boat?

Is the object here to keep the current at a minimum, Im sure SOME of it
will
always go through the hull just because of the motor and the electrical
items
attached to the boat.

Is there anyway to test how much is going through the hull and what is
considered a safe level?

Can someone explain this?
 

Thanks Frank,

Is this just an issue in salt water?
I noticed most of the fasteners on my boat are stainless and it came that way
from the factory. I only use my boat in fresh water and its on the trailer 99%
of the time.

Can someone explain this?
 

Corrosion from fresh water is also a problem, but no where near as severe
as salt water. say 15% or so. In fresh water use magnesium anodes on both
hull and motor. The dis-similar metals of stainless and aluminum will
generate galvanic corrosion when moisture is present. If you have a
stainless prop the problem is worse. Notice I said moisture. It can be from
simple humidity or fog or any other source. The reaction requires very
little water to initialize. It does make for a messy looking boat in a year
or 2. Anodes are cheap protection.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
Thanks Frank,

Is this just an issue in salt water?
I noticed most of the fasteners on my boat are stainless and it came
that way
from the factory. I only use my boat in fresh water and its on the
trailer 99%
of the time.

Can someone explain this?
 

It advised against using the hull as your negative return like they do for
cars where the chasis is used as the negative return.

If the hull is used, current flow through it will create potential
differences across joints and create points for electrolysis action which
will ultimately eat away the hull. Fresh or sal****er only changes the
severity and speed of the electrolytic action.

This is different from bonding where you want to create zero resistance
between metal parts, like the engine and the hull as you described where
there is already electrical contact, a bonding wire is used to
provide/improve the electrical bond. With zero resistance (I mean real
zero, not achieveable in real life) you can eliminate galvanic corrosion
which occurs when 2 dissimilar metals come into contact with each other.
The severity of this corrosion is a function of the 2 material and is
reduced by the effectiveness of the bond.

This corrosion can be diverted through the use of anodes (zinc/magnesium
anodes) where something else is sacrificed. Note that this does not stop
the corrosion, something else takes the brunt of it.

Tan PS


"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the aluminum and
cause
holes in the boat. This is especially important if you are a SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat with
a VOM
and there is definately continuity between the boat and the motor. Whats
the
difference in letting the motor ground to the boat and not the wiring?
What am
I missing here?

Can someone explain this?
 

"Capt Frank Hopkins" wrote
Electrolysis, otherwise known as galvanic corrosion

Begging leave to differ, Capt Frank, but they're two different things. What
you're describing is galvanic action caused when dissimilar metals immersed
in an electrolyte decide to act like a battery and generate electric current
all by themselves. Electrolysis happens when an external source of
electrical current, like your starting battery or shore power supply,
generates electrical current through the water.

Can someone explain this?
 

Entirely true, and they both cause similar damage. We are very familure with
galvanic corrosion in the brine waters of the St. Johns. You can actually
measure the electrical production with a sensitive multimeter. Electrolysis
is a symptom of galvanic corrosion. It degrades the anode metal.

The anode installation and wire bonding fix will take care of both, keeping
your boat pretty.


An interesting experiment.
in a plastic bucket, make some salty water.

place a piece of aluminum foil on one side of the bucket. (top out of
water.)

Place a piece of stainless steel on the other side.(top out of water.)

Set a multimeter to its most sensitive (millivolts) setting and dip one
probe in the center of the bucket. Touch the other probe to the stainless.
record results.

move Aluminum closer to stainless and repeat measurements. record results.

attach a piece of immersed copper wire to aluminum. Allow to stand for 1
day.

Observe stainless steel.

Next

discard salt soulution and rinse container.
place aluminum foil in bottom of bucket.
Mix HOT water with 2 tablespoons of baking soda.
place badly tarnished sterling silver spoon (or other item) so it does not
contact the foil, and measure millivolts from item to water. record results

next make contact with the foil while observing meter. It should spike
sharply and the tarnish jump from the silver to the foil.




--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"Joe Blizzard" wrote in message
...
"Capt Frank Hopkins" wrote
Electrolysis, otherwise known as galvanic corrosion

Begging leave to differ, Capt Frank, but they're two different things.
What
you're describing is galvanic action caused when dissimilar metals
immersed
in an electrolyte decide to act like a battery and generate electric
current
all by themselves. Electrolysis happens when an external source of
electrical current, like your starting battery or shore power supply,
generates electrical current through the water.

Can someone explain this?
 

My outboard has an anode built into the lower unit and it looks fine, is this
enough or should I add one to be safe?

Can someone explain this?
 

You are ok with an anode on the motor, but be sure to add at least 1 to the
hull. 2 would be better. Make sure they are the correct type for freshwater.
Since you keep the boat on a trailer, and use it only in freshwater, I don't
think either electrolysis or galvanic corrosion will be a major factor in
your boat's lifespan. A couple of good coats of wax each season will be more
benefit.

I would electrically bond everything, especially energy using devices'
(lights, radios, fishfinders, ect.) mountings with a separate copper
"ground" wire terminating at the (-) pole of the battery(s). This will give
your devices their best performance and eliminate hot spots in the hull.

Replace freshwater anodes every 24 - 36 months even if they "look ok".

--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
My outboard has an anode built into the lower unit and it looks fine, is
this
enough or should I add one to be safe?

Can someone explain this?
 

Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind of
paint on it. Everything is grounded but I could add a few hull anodes to be
safe. How do hull anodes mount? And where do youI put them for the best
protection?

Can someone explain this?
 

If its the type of paint I think it is, anodes may be unnecessary on the
hull. I would have to see a picture.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind
of
paint on it. Everything is grounded but I could add a few hull anodes
to be
safe. How do hull anodes mount? And where do youI put them for the best
protection?

Can someone explain this?
 

Its like the paint they use on a camo duck boat only one color. Not glossy.
Heavy duty boat, thick aluminum.

Can someone explain this?
 

On 18 Feb 2004 15:46:28 GMT, obull (CCred68046)
wrote:

Its like the paint they use on a camo duck boat only one color. Not glossy.
Heavy duty boat, thick aluminum.

================

If you use the boat in fresh water and store on a trailer, you really
have no reason to worry about electrolysis. Just ensure that your
batteries are turned off when you leave the boat and keep the bilge
dry.
..

Can someone explain this?
 

"CCred68046" wrote in message
...
Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind of
paint on it. Everything is grounded but I could add a few hull anodes to
be
safe. How do hull anodes mount? And where do youI put them for the best
protection?


I have a heavy aluminum boat also. There is an extension of the bottom at
the transom. About 1.5" Allows some tuning of the trim via bending. Mine
has a zinc screwed to the boat on each side on the lip. I can send you an
email pic if you want.
Bill

Can someone explain this?
 

Mine
has a zinc screwed to the boat on each side on the lip. I can send you an
email pic if you want.

OK thats cool, I think I know what you mean but mine does not have anthing like
that and I avoid putting holes in it.

Can someone explain this?
 

"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT.


The key word here is "directly".

What they are saying is that you should NOT use the hull of the boat for
carrying current (remember that this is about aluminum boats).

On a car, it is standard practice to use the frame of the car as the
return lead to the battery. Thus, the wiring harness carries only the
positive side.

On a fiberglass boat you have no choice but to run "ground" wires to
everything. On an aluminum boat, you might consider using the hull of the
boat as a conductor, but it could lead to problems. To start with, aluminum
is not that great of a conductor. Second, every connection is likely to
have a copper to aluminum bond, which puts to dissimilar metals in contact.
Two dissimilar metals plus electrical current can do bad things. Third,
every joint in the hull could suffer from electrolysis.

Note that this is a separate discussion from the electrolysis to the water
problem. There will be those that argue that the hull should be completely
isolated from any electrical source, but that is not an easy thing to
accomplish.

Rod McInnis

Can someone explain this?
 

To start with, aluminum
is not that great of a conductor.

aluminum is in fact a pretty good conductor. Not as good as copper or gold,
but still pretty good. Cheap car jumper cables are often aluminum.

Can someone explain this?
 

On 19 Feb 2004 20:23:18 GMT, (JAXAshby) wrote:

To start with, aluminum
is not that great of a conductor.

aluminum is in fact a pretty good conductor. Not as good as copper or gold,
but still pretty good. Cheap car jumper cables are often aluminum.

Yeah, they used to use it in house wiring also until the CPSC reported
that houses with aluminum wiring were 55 times more likely to have an
electrical fire than copper wired houses.

Bye bye aluminum wiring (in most home applications). It has only a
little more than half the conductivity of copper and really is not that
great of a conductor. It's ok, but I wouldn't use it for anything
important.

Steve

Can someone explain this?
 

"Steven Shelikoff" wrote in message
...
On 19 Feb 2004 20:23:18 GMT, (JAXAshby) wrote:

To start with, aluminum
is not that great of a conductor.

aluminum is in fact a pretty good conductor. Not as good as copper or
gold,
but still pretty good. Cheap car jumper cables are often aluminum.

Yeah, they used to use it in house wiring also until the CPSC reported
that houses with aluminum wiring were 55 times more likely to have an
electrical fire than copper wired houses.

Bye bye aluminum wiring (in most home applications). It has only a
little more than half the conductivity of copper and really is not that
great of a conductor. It's ok, but I wouldn't use it for anything
important.

Steve

Was cheap, was lightweight and caused fires as the aluminum flattens out
under presure from the connection screws. Then a loose connection and fire.
Is still used in high voltage power lines e.g. 500KV, as you can go longer
distances between towers. Still sucks as a conductor, but those bigger
wires can still carry the current and span a longer distance.
Bill

Can someone explain this?
 

On Fri, 20 Feb 2004 00:09:41 GMT, wrote:

On Thu, 19 Feb 2004 23:30:40 GMT, (Steven Shelikoff) wrote:

On 19 Feb 2004 20:23:18 GMT, (JAXAshby) wrote:

To start with, aluminum
is not that great of a conductor.

aluminum is in fact a pretty good conductor. Not as good as copper or gold,
but still pretty good. Cheap car jumper cables are often aluminum.

Yeah, they used to use it in house wiring also until the CPSC reported
that houses with aluminum wiring were 55 times more likely to have an
electrical fire than copper wired houses.

Bye bye aluminum wiring (in most home applications). It has only a
little more than half the conductivity of copper and really is not that
great of a conductor. It's ok, but I wouldn't use it for anything
important.


Apparently you don't have any idea why aluminum wiring in homes was a fire
hazard?

Yeah, I do. It was mostly due to the connections. But the ability to
make good connections is something that I would expect a great conductor
to be able to do. If you can't connect to it, it's not so great.

Steve

Can someone explain this?
 

"Calif Bill" wrote in message
k.net...

"Steven Shelikoff" wrote in message
...
On 19 Feb 2004 20:23:18 GMT, (JAXAshby) wrote:

To start with, aluminum
is not that great of a conductor.

aluminum is in fact a pretty good conductor. Not as good as copper
or
gold,
but still pretty good. Cheap car jumper cables are often aluminum.

Yeah, they used to use it in house wiring also until the CPSC
reported
that houses with aluminum wiring were 55 times more likely to have
an
electrical fire than copper wired houses.

Bye bye aluminum wiring (in most home applications). It has only a
little more than half the conductivity of copper and really is not
that
great of a conductor. It's ok, but I wouldn't use it for anything
important.

Steve

Was cheap, was lightweight and caused fires as the aluminum flattens
out
under presure from the connection screws. Then a loose connection and
fire.
Is still used in high voltage power lines e.g. 500KV, as you can go
longer
distances between towers. Still sucks as a conductor, but those
bigger
wires can still carry the current and span a longer distance.
Bill

It is still widely used, now that the proper connectors have been
developed. The newly installed line from the transformer on the pole to
my house for my upgraded service is Aluminum, as was the old one.
Aluminum has far better conductivity per pound than does copper. It is
also stronger per pound. And it is cheaper.

The problem with Aluminum house wiring was that it oxidizes, and it was
being used with devices designed for copper. It is fine when used with
properly designed devices.

del cecchi

Can someone explain this?
 

Hell, I owned a house that was wired with aluminum. With the right outlets
and switches, it was perfectly fine. With the wrong ones. it was a fire
waiting to happen. The subdivision that I lived in is a few blocks away from
this one and I haven't heard of an electrical fire since it was built in
'75. My buddy is a fireman and he hadn't heard of one either. Lots of
press. Some bad problems, but not as bad as most would make it out to
be...RichG

Can someone explain this?
 

If you do a Google search on "metal + conductivity chart" you will see that
aluminum is one of the better conductors of electricity. The reason they
stopped using it in houses is because of heat cycle failure in circuits that
are switched off and on. In this type of application they will become loose
which will cause even more heat and can pose a serious fire threat. In
applications where the electricity is constantly on it is perfectly suitable
and used in many high voltage applications.

Ask at alt.engineering.electrical if you have any doubts. ;)

Can someone explain this?
 

Damn, now I'm posting off topic!!!!!

Can someone explain this?
 

On 20 Feb 2004 04:55:30 GMT, obull (CCred68046)
wrote:

If you do a Google search on "metal + conductivity chart" you will see that
aluminum is one of the better conductors of electricity. The reason they
stopped using it in houses is because of heat cycle failure in circuits that
are switched off and on. In this type of application they will become loose
which will cause even more heat and can pose a serious fire threat. In

And there's more heat in the first place to cause the heat cycle failure
since aluminum has almost twice the resistance as copper. Thus, it's
not such a great conductor.

applications where the electricity is constantly on it is perfectly suitable
and used in many high voltage applications.

That's because it's a "good" conductor, not a great one. And it's other
properties besides conductivity (light weight) make it more ideal than
copper for high voltage applications. You can rest assured that if
copper were as light as aluminum, they would be using that instead.
Utilities don't like loosing all that energy to wasted heat if they
don't have to.

Ask at alt.engineering.electrical if you have any doubts. ;)

No doubts here.

Steve

Can someone explain this?
 

On Thu, 19 Feb 2004 21:47:41 -0600, "del cecchi"
wrote:

It is still widely used, now that the proper connectors have been
developed. The newly installed line from the transformer on the pole to
my house for my upgraded service is Aluminum, as was the old one.
Aluminum has far better conductivity per pound than does copper. It is
also stronger per pound. And it is cheaper.

That's only because it's so light, not because it's such a great
conductor. In applications where it has to be suspended, like high
voltage lines or the feeder line to your house, it's fine. But if you
don't have to suspend it, like boat, house or car wiring, you're better
off with the higher conductivity of copper.

Even in applications where weight is critical, such as spacecraft,
aircraft, etc., they use copper instead of aluminum. For instance, the
international space station has many miles of electrical wire. Think of
all the weight savings and cost savings that could have been had by
using aluminum. The structural components are aluminum but the wiring
is copper despite Al's better conductivity per pound. There's a reason
for that... because it's not a great conductor.

Steve

Can someone explain this?
 

On Fri, 20 Feb 2004 04:23:20 GMT, "RichG"
wrote:

Hell, I owned a house that was wired with aluminum. With the right outlets
and switches, it was perfectly fine. With the wrong ones. it was a fire
waiting to happen. The subdivision that I lived in is a few blocks away from
this one and I haven't heard of an electrical fire since it was built in
'75. My buddy is a fireman and he hadn't heard of one either. Lots of
press. Some bad problems, but not as bad as most would make it out to
be...RichG

That's not true either. The problems were a lot less when they started
using the proper connectors. But they still persisted and so most
municipalities now don't allow aluminum house wiring. Some do, most
don't.

Steve

Can someone explain this?
 

.
Aluminum has far better conductivity per pound than does copper.

True, but it's much bulkier. An aluminum wire has to be much bigger than a
copper wire, if both are rated to carry the same wattage

... It is
also stronger per pound. And it is cheaper.

Not in marine grades, it isn't.



Steven Shelikoff wrote:
.... in applications where weight is critical, such as spacecraft,
aircraft, etc., they use copper instead of aluminum.

In a lot of aviation applications, and for sensitive instruments, platinum &
gold are used. Clearly not where cost is an issue though ;)

DSK

Can someone explain this?
 

"Steven Shelikoff" wrote in message
...
On Thu, 19 Feb 2004 21:47:41 -0600, "del cecchi"
wrote:

It is still widely used, now that the proper connectors have been
developed. The newly installed line from the transformer on the pole to
my house for my upgraded service is Aluminum, as was the old one.
Aluminum has far better conductivity per pound than does copper. It is
also stronger per pound. And it is cheaper.

That's only because it's so light, not because it's such a great
conductor. In applications where it has to be suspended, like high
voltage lines or the feeder line to your house, it's fine. But if you
don't have to suspend it, like boat, house or car wiring, you're better
off with the higher conductivity of copper.

Copper is 2.7/1.7 or 1.58 times a better conductor. So a wire would have to
have a diameter 1.26 times as great in aluminum. However the density is
8.96/2.7 or 3.3 times as high for copper so a copper wire with the same
resistance weighs twice as much.

Aluminum is .78/1.3 or .6 times as expensive, so to net it out, a copper
wire costs about 3.5 times as much for the material as does an aluminum wire
for the same resistance.

Even in applications where weight is critical, such as spacecraft,
aircraft, etc., they use copper instead of aluminum. For instance, the
international space station has many miles of electrical wire. Think of
all the weight savings and cost savings that could have been had by
using aluminum. The structural components are aluminum but the wiring
is copper despite Al's better conductivity per pound. There's a reason
for that... because it's not a great conductor.

Steve

I would guess that space in the wiring areas and mechanical properties are
most important in the space station. In boats, corrosion resistance. These
could both favor copper over Al.

del cecchi