Water Cooled Power Resistor Gets Rusty

[D from BC]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

 

[Phil Allison]

"D from BC"

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

** All you need do is coat the terminals and any exposed metal that is
submerged with something waterproof.

Use shrink on tubing, silicone adhesive and/or spray on lacquer to seal it
up.

I had much the same problem with tubular WW dummy load resistors used to
test power amplifiers but have managed to make them last many years.

Forget using oil - far too damn dangerous.

If it don't smoke and catch fire, it will spill sometime and burn YOU like
hell.




........ Phil

 

[ChairmanOfTheBored]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

Use 3M's "Fluorinert" dielectric fluid.

FC-40 first one on the list.

http://products3.3m.com/catalog/us/...oilgas_3_0/command_AbcPageHandler/output_html

1500V per mil breakdown strength.

As soon as your water gets into contact with those metals, it becomes
ionized water.

 

[Stanislaw Flatto]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

Should post to plumbing.sci.
We don't repair umbrellas.

Stanislaw.

 

[neon]

Well unless the water is circulating i don't see any benefits from the water immersion. If this is your case you are better off with a fan to remove heat then water. Heat must go somewhere for cooling.

 

[Ecnerwal]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Surprise, surprise...not.

I dunno...maybe these ions might do some funky electrolysis.

Not to mention messing with the resistance. When you want a serious (but
not altogether stable itself) resistive test load, just stick a couple
of copper electrodes in a copper sulfate solution - it's what we used to
do at the lab for making BIG power resistors.

Or just give up on water and go to icky oil

One of my least favorite memories of lab work would be working in marx
generator tanks dripping with oil.

Pharmacy mineral oil?

Should be fairly benign.

Nichrome from an old toaster or heater in a box (to keep you from
touching the live wires) with alligator clips is a nice adjustable test
load that works fine when air-cooled, so it's nice and clean and
non-icky.

A few ordinary 25-50W air-cooled power resistors and some switches to
configure the bank could also work, though the resistors are rather
expensive if not found surplus.

 

[Jim Yanik]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

most people cool their power resistors in mineral oil.
That is also what my USAF cal lab(PMEL) kept their standard resistors in.
It can get a bit messy,though.

 

[G]

most people cool their power resistors in mineral oil.
That is also what my USAF cal lab(PMEL) kept their standard resistors in.
It can get a bit messy,though.

The old Heath Cantenna, used mineral oil.

I made up some fixtures with screw on resistors and heat sinks, with the
capability to use a fan.


greg

 

[Phil Allison]

"Jim Yanik"

most people cool their power resistors in mineral oil.

** Only if the load is for RF use and there is a safety temp cut out.




...... Phil

 

[Phil Allison]

"G"

The old Heath Cantenna, used mineral oil.

** A dummy 'antenna ' by name and use.

I made up some fixtures with screw on resistors and heat sinks, with the
capability to use a fan.

** Very expensive and tends to stink the room out when it gets hot & there
is any dust on the parts.

A water submerged, tubular WW resistor never smells or catches fire,
dissipates huge amounts of power & self temp limits to just over 100C -
keeping the resistor value accurate.




....... Phil

 

[Tam/WB2TT]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

Commercial liquid cooled loads, like Heathkit and MFJ, use oil. Supposedly
transformer oil is best, followed by mineral oil. I knew of one person who
used automatic transmission fluid. Antifreeze may or may not work. The ones
I mentioned are built into unused gallon size metal paint cans. You should
be able to find a lot of info if you do a search on Cantenna.

Tam/WB2TT

 

[Jamie]

I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting.

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite)

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice..
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC

how about using mineral or transformer oil instead?

 

[Phil Allison]

"Tam/WB2TT"

Commercial liquid cooled loads, like Heathkit and MFJ, use oil.

** Realise that is because you CANNOT use water for a radio frequency dummy
load.

The OP is not restricted to using a bad and highly DANGEROUS heat
absorber like oil.




......... Phil

 

[Spehro Pefhany]

how about using mineral or transformer oil instead?

How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).


Best regards,
Spehro Pefhany

 

[Straw Man]

How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).

I use Olive oil and Balsamic vinegar.

 

[Spehro Pefhany]

I use Olive oil and Balsamic vinegar.

It's a heat transfer medium *and* a salad topping.


Best regards,
Spehro Pefhany

 

[D from BC]

Use 3M's "Fluorinert" dielectric fluid.

FC-40 first one on the list.

http://products3.3m.com/catalog/us/...oilgas_3_0/command_AbcPageHandler/output_html

1500V per mil breakdown strength.

As soon as your water gets into contact with those metals, it becomes
ionized water.

It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert

It's going to be exxxxpennnsive....
D from BC

 

[D from BC]

Reading all replies... (thanks all by the way..)

Water Vs Mineral Oil

Water Pros
Off the tap.
100C bp is commonly known
Non toxic liquid
Non toxic steam
Odorless
Higher specific heat capacity than mineral oil.

Water Cons
Corrosion of ferrous terminals
Ion content increases with rusting and leads to electrolysis erosion
due to exposed terminals at 100VDC.

Mineral Oil Pros
No corrosion.
Obtained at pharmacy.
No electrolysis at 100VDC.

Cons
Possibly more resistance error due to higher boiling point.
bp ~360C??

Vapors can ignite with spark (flash point) around 145C to 193C??.

(See movie of a fire ball from an exploding mineral oil transformer on
http://205.243.100.155/frames/longarc.htm#Blowup )

Lower specific heat capacity than water.

Oil vapor coating everything.. Yuck.

Oil smell.


Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
It'll rust but not erode due to electrolysis (the other terminals are
coated.)
So if electrolysis can't take place then maybe I can try out Vitamin
C..
I'm no chemist but I'm dying to try Vitamin C as a corrosion
inhibitor. It's got that "fun with chemistry" appeal..
My steaming power resistor may have a nice zippy smell too

But ..if the coating fails on the other terminals ...just one
microscopic crack or hole and I think the electrolysis will start
peeling the coating and lead to even more electrolysis.

Seeing Vitamin C getting electrolyzed will be new

The device under test is safe to overload..so if I get a liquid short
out..it's ok...


D from BC

 

[whit3rd]

I have a big O wirewound resistor I keep cool in a container of water.

[100 ohm adjustable, 100W range]

The terminals and tap are rusting.

You can use several solutions: exchange the water for a nonionizing
fluid
(mineral oil with high flashpoint is cheap, transformer oils and
fluorinert
are also available), or just lower the water's corrosivity (add rust
inhibitor
from the auto parts store to deionized water), or use resistors that
are water-safe.

Every electric water heater, from tea kettles to home hotwater tanks,
has such an immersible resistor. Some have several. One here in my
junkbox
is rated at 4500W at 240VAC - so it's 12.8 ohms. Eight of those,
and you can pick resistances from 1.5 to 100 ohms with no rust.

 

[D from BC]

I have a big O wirewound resistor I keep cool in a container of water.

[100 ohm adjustable, 100W range]

The terminals and tap are rusting.

You can use several solutions: exchange the water for a nonionizing
fluid
(mineral oil with high flashpoint is cheap, transformer oils and
fluorinert
are also available), or just lower the water's corrosivity (add rust
inhibitor
from the auto parts store to deionized water), or use resistors that
are water-safe.

Every electric water heater, from tea kettles to home hotwater tanks,
has such an immersible resistor. Some have several. One here in my
junkbox
is rated at 4500W at 240VAC - so it's 12.8 ohms. Eight of those,
and you can pick resistances from 1.5 to 100 ohms with no rust.

Neat...
I can picture myself filling a shopping cart full of used water
heaters at the local thrift store..

D from BC