Corrosion in magnet gap of 10" RCF driver, recoverable or replacement only option?
Hi all, interested in people's opinions on this, bad corrosion in magnet gaps causing coil rubbing etc.
Has anyone ever successfully (by successfully I mean reliably) repaired this kind of damage before reconing a driver?
I realise it's obviously possible to remove the corrosion with a lot of care, but surely when something starts to corrode then it will just continue sooner rather than later even if removed to start with.
Is it sensible to try to clean up this damage, maybe treat it with something to help prevent it returning, and then spend a fair amount of money on 4 recones? Or is not worth the risk and new replacement drivers the only sensible option?
The repair needs to be reliable not a bodge (needs to last for years)
Thanks Jim
Hi all, interested in people's opinions on this, bad corrosion in magnet gaps causing coil rubbing etc.
Has anyone ever successfully (by successfully I mean reliably) repaired this kind of damage before reconing a driver?
I realise it's obviously possible to remove the corrosion with a lot of care, but surely when something starts to corrode then it will just continue sooner rather than later even if removed to start with.
Is it sensible to try to clean up this damage, maybe treat it with something to help prevent it returning, and then spend a fair amount of money on 4 recones? Or is not worth the risk and new replacement drivers the only sensible option?
The repair needs to be reliable not a bodge (needs to last for years)
Thanks Jim
fine emery, a good vacuuming, a polish with cardstock and some rust converter/inhibitor and voila... if it where not possible i would have sent many a driver frame to an early grave, touring pa's see a lot of adverse climate conditions and corrosion is inevitable...along with beer swill...
That's interesting thanks. I'll look into what you have mentioned and maybe try it out on one of the drivers (I have actually bought two recone kits before I found this damage, so might has well try one)
It is the medium / long term effect that I am concerned about, I know I can recone it so it is free to move after the recone, but then it would be relying on the rust convertor chemicals but if you have direct experience of this then that increases my confidence.
Do you mind asking what was the exact product you used to inhibit the rust re-forming?
Thanks very much, Jim
It is the medium / long term effect that I am concerned about, I know I can recone it so it is free to move after the recone, but then it would be relying on the rust convertor chemicals but if you have direct experience of this then that increases my confidence.
Do you mind asking what was the exact product you used to inhibit the rust re-forming?
Thanks very much, Jim
Rust Check Rust Converter, Bottle, 236-mL | Canadian Tire
this is what i used after removal and cleaning.
this is what i used after removal and cleaning.
Thanks for the suggestion I'll look into the chemicals.
They are out of an old EAW KF600i rig that was stored by someone in flightcases in a damp place for years
They are out of an old EAW KF600i rig that was stored by someone in flightcases in a damp place for years
Steel hates damp so that explains why they rusted.
A very fine emery paper will remove the rust ok.
Rust tends to expand so will reduce the gap.
Not sure about "rust remedies" painted on as they will decrease the gap if not a very thin layer.
Above suggestions by turk and nigel very good.
Let me add my version:
1) rust occupies more volume than original iron, so it´s not enough to convert it but also to remove it to leave VERY TIGHT gap space free.
2) so sanding is needed.
Let me add that sanding inside the gap is very difficult plus you must keep plate hole and polepiece concentric.
I suggest you get a piece of relatively firm carboard, sandwiching 2 or 3 cereal box type sheets is fine, until you *almost* reach gap thickness, then a similar piece of grit 400 wet or dry emery paper makes for the full thickness.
The idea is to sand "mountains" off without eating also rhe "valleys" and unduly enlarging gap.
Every few passes vacuum the gap and then wipe with a piece of sticky tape (painters´paper type is perfect) to remove oxide dust still sticking to gap walls.
Do it as many times as needed as to allow a clean piece of stacked cardboard built up to slightly more than gap width can slip around full 360 deg turn keeping basically same friction, that is your "thickness gap".
3) Once you have mechanically removed rust and returned dimensions to normal, then you convert remaining rust in pits and free metal surface (you have already ground zinc plating off) to stable iron phosphate.
Above suggested product is very good.
Wipe rusted area with a Q tip or similar soft applicator, inside gap with a piece of folded cloth with a piece of plastic in the middle to add some rigidity.
Take your time and do it bit by bit: just wet cloth, wipe, let it act 15 minutes, wipe again, you want a pearl grey surface with some "whitish dust" on it, which is converted oxide.
Let it sit overnight and recheck next day, repeat if needed.
Finally wipe with clean cloth and a little distilled water to pull acid residue and dry with a heat gun.
Remaining surface is very stable and best you can get at home, speaker can be safely reconed and enjoyed.
You will not be able to paint over it, replate or oil/grease surface but in a relatively dry environment phosphatized surface alone will stand years, justifying reconing.
Just as a side note: the PRO solution is to send drivers to a real PRO reconer who will demagnetize and disassemble magnetic circuit, send iron parts to a zincplater who in the process will remove all rust for good and replate, and then reassemble and remagnetize, but I guess you won´t go that far.
As a side note: I make commercially speakers and my usual finish/protection is zinc plating, avoid paint and specially epoxy paint which steal too much gap space, but *sometimes* I had to send a few urgent samples and only had time to phosphatize and assemble, or best case spray a *thin* coat of car type grey primer over it ... they are working as well as the plated ones after many years, go figure.
As long as they don´t get in the rain or dripping wet with condensation that is.
Let me add my version:
1) rust occupies more volume than original iron, so it´s not enough to convert it but also to remove it to leave VERY TIGHT gap space free.
2) so sanding is needed.
Let me add that sanding inside the gap is very difficult plus you must keep plate hole and polepiece concentric.
I suggest you get a piece of relatively firm carboard, sandwiching 2 or 3 cereal box type sheets is fine, until you *almost* reach gap thickness, then a similar piece of grit 400 wet or dry emery paper makes for the full thickness.
The idea is to sand "mountains" off without eating also rhe "valleys" and unduly enlarging gap.
Every few passes vacuum the gap and then wipe with a piece of sticky tape (painters´paper type is perfect) to remove oxide dust still sticking to gap walls.
Do it as many times as needed as to allow a clean piece of stacked cardboard built up to slightly more than gap width can slip around full 360 deg turn keeping basically same friction, that is your "thickness gap".
3) Once you have mechanically removed rust and returned dimensions to normal, then you convert remaining rust in pits and free metal surface (you have already ground zinc plating off) to stable iron phosphate.
Above suggested product is very good.
Wipe rusted area with a Q tip or similar soft applicator, inside gap with a piece of folded cloth with a piece of plastic in the middle to add some rigidity.
Take your time and do it bit by bit: just wet cloth, wipe, let it act 15 minutes, wipe again, you want a pearl grey surface with some "whitish dust" on it, which is converted oxide.
Let it sit overnight and recheck next day, repeat if needed.
Finally wipe with clean cloth and a little distilled water to pull acid residue and dry with a heat gun.
Remaining surface is very stable and best you can get at home, speaker can be safely reconed and enjoyed.
You will not be able to paint over it, replate or oil/grease surface but in a relatively dry environment phosphatized surface alone will stand years, justifying reconing.
Just as a side note: the PRO solution is to send drivers to a real PRO reconer who will demagnetize and disassemble magnetic circuit, send iron parts to a zincplater who in the process will remove all rust for good and replate, and then reassemble and remagnetize, but I guess you won´t go that far.
As a side note: I make commercially speakers and my usual finish/protection is zinc plating, avoid paint and specially epoxy paint which steal too much gap space, but *sometimes* I had to send a few urgent samples and only had time to phosphatize and assemble, or best case spray a *thin* coat of car type grey primer over it ... they are working as well as the plated ones after many years, go figure.
As long as they don´t get in the rain or dripping wet with condensation that is.
That reads like some good advice. Hope I don't need it, but I would add a wipe with water and baking soda (base) to neutralize and remove the acid residue and then wipe it with distilled water.
Thanks to everyone for their advice, I think in this case (these 4 x 10" drivers) I will buy new because the corrosion is very bad.
However, from the same cabinets I have 4 x 15" RCF drivers where the corrosion is nowhere near as bad, there are only a few spots. Also, in these 15" drivers, the pole piece is copper-clad, so is offering protection there.
So I may go ahead and try the above treatments and recones with these drivers which are both more expensive and in a much better condition to start with.
Thanks all for your advice 🙂
However, from the same cabinets I have 4 x 15" RCF drivers where the corrosion is nowhere near as bad, there are only a few spots. Also, in these 15" drivers, the pole piece is copper-clad, so is offering protection there.
So I may go ahead and try the above treatments and recones with these drivers which are both more expensive and in a much better condition to start with.
Thanks all for your advice 🙂
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