Whilst stripping and spraying the lathe I’ve had the need to remove oil, grease and paint from a number of parts. Most of these have been small and made from some form of alloy and so have had to have either been bead blasted (none with bearing surfaces) or chemically stripped using a product called “Tergo Strip”. This stuff is amazing, brush it on and then watch the paint flake off. Spray with a waterblaster, dry, scrub with detergent, dry and then paint.
The Lathe bed however has proved to be a different mission however with the paint on this part proving to be a lot more of a pain to remove. The ways mean that bead blasting is out of the question and the requirement to wash Tergo strip off with water opens the door to flash rusting in all sorts of places (this part is not made of alloy). Combine that with the fact that the thing weighs at least a good 40 kg and there’s a problem.
The solution proved to be electrolytic rust removal, a process that seems to be so simple and so effective that I’m still slightly suspicious of it. Basically you suspend the rusty part in a container of water + washing flakes (sodium carbonate), hang a piece of iron in there as well, connect a battery charger to the rusty part and the chunk of iron and watch the rust disappear.
My implementation of this process started with a 160L plastic drum purchased off Trademe, some rebar and a computer power supply. The rebar was cut into 6 lengths, had the ends ground clear of any rust and dirt and then hung around the perimeter of the drum.
Copper wire was then would around the ends of the rebar and taped to stay in place.
Four Square provided a box of 44% soap flakes which was then dissolved in 10L of hot water before being poured into the drum with cold water from a hose.
The Lathe bed was hung from the roof initially with a ratchet tie-down and then using a spare boat winch to facilitate easy removal for inspection. Car jumper leads then provided the connection between the computer power supply GND and +12v1 rail and the lathe bed and copper / rebar ring.
Powering the power supply on results in a slight fizzing sound and bubbles on both the lathe and the rebar (hydrogen and oxygen apparently). 5 minutes of bubbling results in rust scum such as this,
with a further hour resulting in this cocktail
Initially the current through the system was higher than was preferable so some of the solution was siphoned off and replaced with fresh water.
Already the paint has started to flake off and any areas that had developed slight rusting have come clean which is very promising. I plan to remove the lathe later tonight after soaking for most of the day and give it a good scrub before replacing it for another soak.
After that it will be a case of cleaning it off and displacing the water in a manner that will allow me to repaint (not sure on this one yet) before masking and getting a base coat on it.
On the arcade front the woodwork is pretty much finished, just waiting on the door that needs to be installed in one side before painting.
The LCD mount ended up a bit different to that in the plans, basically the screen sits on the mount below with the help of a 3D printed VESA mount. The bolts allow the screen to be screwed up and down whilst the threaded rod allows for positioning on one axis.