Firstly, excuse me cutting up your original post, it's just so I keep a logical order.....
With the wire mesh I had placed it under to face the main surface and around the edges. Lots of visible action but the wire mesh was too fine and disintegrated. My original thought for mesh was that it would provide more actual surface area than a metal sheet. Currently still running but using some much heavier expanded metal under. I see less bubbling but the reaction is ongoing.
Sounds about right, I couldn't tell from the photo. Basically I'd want to space it as close as possible and all around the surface I wanted to clean. For something like that I'd expect to do it in several stages, moving the anode to the bit I wanted to attack. I agree, expanded metal will give a larger surface area although I think with more area your current density will drop for a given input. The other snag is that the expanded area gives more opportunities for it to corrode ! Maybe try something like copper or stainless sheet ? I don't know, that's a pure stab in the dark.
What I am not satisfied with is the removal of heavy scale between layers and inside the box section.
Perhaps acid would get to that in a timely manner?
Personally I doubt it will remove scale between two layers of a steel sandwich if that's what you're hoping. It'll clean up the outsides great but access for electrolyte down the crevice will be poor and that's what you'll need to remove scale. It could do it but without some brushing/circulation it'll take ages.
The same circulation problem between layers applies for acid as well, in fact I can't think of a good way of ensuring it's clear. Acid would be worse because you'd have to make double sure you'd got everything out and that would be difficult.
The box section has similar problems of getting the anodes in the best place and although it will work you'll have the outsides sparkly clean before the insides get moving. I think you've started with the hardest possible part of the car to do !
In any case the pitting, thinning, and gaps, have convinced me to try to just replace the T section. I will use this process again on smaller parts but have to consider it a fail for closed in areas. Maybe it would succeed eventually?
I'd second that, if there's any significant rusting then I give up trying to clean & paint, I simply cut out metal and replace with new.
There was light surface rust inside the crossmember when I repaired my chassis and all I did was clean as much as possible then cover the area with waxoyl, a non-drying waxy underseal, to keep air/moisture away. Providing it doesn't get washed off with road spray (as it would on the uprights/outer surface for example) it's done a great job in arresting corrosion. Every now and then when I think about it I'll spray a bit more through the access holes but that's probably overkill/wasteful.
But even if you do end up repairing/replacing the front section, the big positive is that you've sorted out the process and have something that will be excellent for cleaning things like the vertical links and suspension parts. Probably good for calipers as well ?
Brian
