Hello guys,
lets give you a short update to that what I did, because meanwhile I cleaned my rims as mentioned.
But to remember to the reason of this thread, first a screenshot to the situation how it was at the beginning of the cleaning procedure:
Now the procedure itself:
First I used oxalic acid (2 coffee spoons of the acid powder in 250 milli liters of warm water) to remove the oxide spots on the sand casted surface. Then I cleaned everything with a brush and a lot of water to get rid of the acid residuals. For the areas that were unreachable with the brush I used a small electric hand grinder with little plastic brushes.
Then, I cleaned the machined surfaces with a cleaning fleece that is typically also used for copper pipes before they will be soldered. After that, I removed the remaining slight differences in brightness on the casted surfaces that were still visible with a glass fiber eraser, someone of you possibly know this eraser from former times where technical drawings were made by hand with ink on parchment or foil.
This glass fiber eraser works pretty good, I never would have never expected that, especially on small surfaces with many details.
And this is the result:
... almost as new - I am happy!
By the way - let me wish you all and also your families Merry Christmas!
Werner