Aluminium cleaning advice please.

[Amie]

Hi all.
I have a couple of tuning capacitors that are heavily soiled and with somewhat corroded vanes that I need to clean.

I have to hand some automotive aluminium cleaner, (Alubrite = phosphoric acid), has anyone had any experience of using this kind of cleaner for this job?

Thanks.
Amie.

[ppppenguin]

I haven't tried this myself, but I've seen good reports of putting them in the dishwasher. Assuming you have one. The detergent is strongly alkaline which will be good for cleaning ali. For doing them by hand I'd start with ordinary washing soda (sodium carbonate, not the same as baking powder which is sodium bicarbonate) and agitate well in a hot solution. Wear rubber gloves. If you have an ultrasonic cleaner then hot washing soda solution in that should work very nicely.

Caustic soda (sodium hydroxide) will certainly clean ali but it's a bit too vicious for a first attempt. Leave it too long and you'll have no ali at all

In any case, you will need to relubricate the bearings after cleaning.

All of the above is a bit theoretical. I've cleaned ali before, but never had to do a tuning cap, so it would be good to hear from those who've done it in real life.

[boater sam]

All good info,  but if you etch the plates too much, the value of the capacitor will be affected. Go steady.

[ppppenguin]

Crud on the plates can also affect the value by acting as a dielectric. Might be interesting to measure max/min capacitance before and after cleaning.

[Nick]

I have cleaned these in an ultrasonic bath using slightly alkaline industrial detergent (Tikopur R33)

Came up extremely well - only leave in for about 5 minutes as ultrasonic cleaners are surprisingly aggressive.

This one is from a DAC90A and was thick with dirt & nicotine before cleaning...

   

[Murphyv310]

I'd not use acid.
Diluted TFR will do the job.
See my Soviet tv thread and the result on the valve screening Dan's.

[ppppenguin]

I'd not use acid.
Diluted TFR will do the job.
See my Soviet tv thread and the result on the valve screening Dan's.

TFR?

[Murphyv310]

Traffic Film Remover.
It's alkaline but too caustic to use neat. Try 10% first.
Go to any of the Polish car valet chaps and they'll fill a little bottle for a few Bob.
In fact if you look at the smoothing cans on the Soviet set you'll see how good they come up, that's with a 10% solution via a foam bottle.
TV22 chassis come up like brand new with this treatment.

[Murphyv310]

Incidentally not all types of TFR are greatly caustic, the ones I use are low.
Even dipping alloy I a solution of bicarbonate of soda will remove a microscopic layer from aluminium.

[ppppenguin]

Do you mean bicarbonate or carbonate? Both are alkaline in solution but sodium carbonate is probably a bit stronger. Both are cheap and easy to get.

I looked up TFR and its alkaline content can either be from caustic soda or sodium metasilicate.