my rust removal tank

[123hotchef]

its the lamp giving that voltage drop take the lamp out and the voltage at the tank is 11.98

 

[The_Yellow_Ardvark]

Change the bulb
I only keep a 5a use in line.
I tend to use a 12V(of Load) PSU, as long as I get volts through the circuit I am happy.

 

[123hotchef]

how do i work out what bulb I need to use? I am thinking I need a smaller Watt bulb

 

[The_Yellow_Ardvark]

yes simply. or be brave and fit a variable resister.

 

[123hotchef]

i have a load of 12v 4W and 12v 5W bulbs might try one of those first

 

[WorkshopChris]

Give it a try its just a case of protecting your power supply while providing enough current to remove rust.
You have a few variables you can alter till you get the best result.

 

[123hotchef]

I will try and report back seems like the indicator lamp was sucking all the juice

 

[DAPPH]

hey good shout i did put 1kg the whole bag into the cwst about 25 galons

I used 100 gram of washing soda in about 25 gallons of water and an old 1960's Halfords battery charger running at 12 volt 4 amps initially which tapered down to about 1/2 amp after four days ..

After de-rusting several things the re-bar electrodes I've used are nearly double the circumference with rusticles and bits of removed zinc plating etc. To clean them easily & quickly I power washed them off at 150 bar as I was also using it for other things . ... That worked ...... but not as good as when I used a power drill and a rotary cup wire brush to clean them up .

 

[123hotchef]

100 grams of soda to 25 gallons so i have a 10 times stronger solution than u

 

[123hotchef]

I have to resurrect this thread

My rust tank was working but now when I turn the power supply on the volts drop off to just under 2V disconnect the cables and it puts out 13V, whats going on

 

[123hotchef]

that is another thing when it was working ok it would draw just over 3 amps with a lamp in the loop I had it drawing 1.5 amps if the metal is clean does the draw drop off?

 

[MattF]

Current draw is dependent on many factors. Just make sure to clean any loose stuff of the anodes and make sure all connections are good, and leave it to it. Doesn't really matter what voltage or current draw you're seeing on the gauges, as long as it is drawing some current. If you can see bubbles coming off the piece, you're good.

 

[123hotchef]

it is worrying that the led on the power supply goes dim and the voltage goes down when I connect it though

 

[Screwdriver]

If the volts are dropping, the circuit is drawing too much current.

Your setup looks really good but are you sure the plastic tank isn't also conductive? If it's a glassfibre tank it might well conduct when it gets wet and some plastics also can conduct.

A bulb in series will do nothing to limit current, that's an old wives tale. All it will do is light up and tell you if the power is on! A bulb is not an active component, all it does is dissipate energy. If you connect 12v across a 12v bulb rated at say 20w then it will dissipate 20w of energy. Bump the volts up to 24v and the same bulb will dissipate 40w except the rating generally tells you how much power a bulb can dissipate before it blows up!

Secondly, people use a bulb to "limit" current, when all they are actually doing is moving the useful energy from your tank into the bulb. The same total current will flow. So if you want to limit the total current you need to increase the resistance of your tank or lower the voltage. Much easier to increase the resistance of the tank by just not putting so much electrolyte in it. For a bucket that size, I'd start with a cup, maybe two cups of washing powder (i.e. one containing sodium carbonate).

Anything more than an amp at 12v is a waste of energy. You want to cajole those iron oxides from the cathode there's no need to rip them off unless you're in a hurry. It looks great when everything is bubbling and fizzing away but the more gentle process gives the better result. Higher currents do not allow the reduced iron molecules to bond as strongly with the surface being de-rusted. Net result is much more deterioration of the workpiece and higher currents will destroy any fine detail that may have survived under all that rust.

So: check the tank is non conductive and use less electrolyte. You can safely start the process without any and just add it until you get just over an amp flowing.

Stick a bulb in series if you want top light up the garden. it will do nothing else for you...

 

[Screwdriver]

Yes, what you are talking about is a situation where the load i.e. an LED has a complex resistance which varies with voltage. Typically this very (very) low resistance would allow way too much current to flow so you use a resistor in series, typically 100 times higher than the nominal "resistance" of an LED. Almost all of the voltage drop is across the resistor.

In this case the load is a bucket of electrolyte with an unknown resistance but probably circa 20ohms (i.e 1A @ 12V). But most importantly, you are not connecting a simple DC source like a battery, most people are using a constant current source like a battery charger. Without some deeper knowledge of how the output of that charging circuit has been designed, you really can't tell what difference an additional load (like a simple bulb) is going to make,

On the other hand, a PC power supply is more likely to be designed to operate as a constant voltage source. Again, you have no idea what an additional load will do under those circumstances.

So in practical terms, unless you are using a simple battery to drive this circuit, a bulb in series with the electrolysis bucket is literally a waste of energy and it is MUCh easier to moderate the total current flow by varying the resistance of the load by varying the concentration of electrolyte.

 

[Screwdriver]

A standard car battery charger (transformer and rectifier) isn't a constant current source.

Most lead acid chargers are because otherwise they would have to deliver the rated capacity of a battery if you connect it to a flat battery.

So if you have an 80 ah flat battery, an unregulated charger would try to dump 80 amps into it!

 

[123hotchef]

I am using a CB power pack I also tried a spare power pack and got the same going ons

the draw was measured with my multi meter

The lamp no longer illuminates either but it has not blown

 

[123hotchef]

Yes, what you are talking about is a situation where the load i.e. an LED has a complex resistance which varies with voltage. Typically this very (very) low resistance would allow way too much current to flow so you use a resistor in series, typically 100 times higher than the nominal "resistance" of an LED. Almost all of the voltage drop is across the resistor.

In this case the load is a bucket of electrolyte with an unknown resistance but probably circa 20ohms (i.e 1A @ 12V). But most importantly, you are not connecting a simple DC source like a battery, most people are using a constant current source like a battery charger. Without some deeper knowledge of how the output of that charging circuit has been designed, you really can't tell what difference an additional load (like a simple bulb) is going to make,

On the other hand, a PC power supply is more likely to be designed to operate as a constant voltage source. Again, you have no idea what an additional load will do under those circumstances.

So in practical terms, unless you are using a simple battery to drive this circuit, a bulb in series with the electrolysis bucket is literally a waste of energy and it is MUCh easier to moderate the total current flow by varying the resistance of the load by varying the concentration of electrolyte.

I did think it was too concentrated!

 

[123hotchef]

If the volts are dropping, the circuit is drawing too much current.

Your setup looks really good but are you sure the plastic tank isn't also conductive? If it's a glassfibre tank it might well conduct when it gets wet and some plastics also can conduct.

A bulb in series will do nothing to limit current, that's an old wives tale. All it will do is light up and tell you if the power is on! A bulb is not an active component, all it does is dissipate energy. If you connect 12v across a 12v bulb rated at say 20w then it will dissipate 20w of energy. Bump the volts up to 24v and the same bulb will dissipate 40w except the rating generally tells you how much power a bulb can dissipate before it blows up!

Secondly, people use a bulb to "limit" current, when all they are actually doing is moving the useful energy from your tank into the bulb. The same total current will flow. So if you want to limit the total current you need to increase the resistance of your tank or lower the voltage. Much easier to increase the resistance of the tank by just not putting so much electrolyte in it. For a bucket that size, I'd start with a cup, maybe two cups of washing powder (i.e. one containing sodium carbonate).

Anything more than an amp at 12v is a waste of energy. You want to cajole those iron oxides from the cathode there's no need to rip them off unless you're in a hurry. It looks great when everything is bubbling and fizzing away but the more gentle process gives the better result. Higher currents do not allow the reduced iron molecules to bond as strongly with the surface being de-rusted. Net result is much more deterioration of the workpiece and higher currents will destroy any fine detail that may have survived under all that rust.

So: check the tank is non conductive and use less electrolyte. You can safely start the process without any and just add it until you get just over an amp flowing.

Stick a bulb in series if you want top light up the garden. it will do nothing else for you...

Great information thank you very much I will take half of my solution out and top it back up with clean water. I will also check the tank for continuity then, I dont think it is conductive it is a CWST the black plastic type but it could be, it is weird it was working fine for weeks

 

[MattF]

it is worrying that the led on the power supply goes dim and the voltage goes down when I connect it though

Do you currently have the ammeter in line to see what current is being drawn? If it's still within the <3A range, that would likely indicate your PSU is faulty. If far more current is being drawn, something is likely shorted.