Thought the old merc owners on here would find this useful as well as those with other 70's/80's cars with aluminum rather than chrome trim.
From here:
W123 Group on MSN
WARNING: Caustic soda causes burns. be careful. Wear rubber gloves, because you won't feel the pain until you rub your eyes.
To clean the aluminium trim blades - that become discoloured - running down the rear windows, you will need: a mild solution of sodium hydroxide (caustic soda), loads of cotton buds, paper towels, Brasso metal polish or similar, loads of time, and to realise that you are actually irreversibly damaging the trim, even if it does come up nice. The caustic soda dissolves the lacquer and de-anodises the aluminium, so you have to do it very slowly. Apply with cotton buds; you will see the liquid become frothy as the lacquer comes away and turns streaky, you need to use cotton buds to keep it under control. Wipe as you go and don't leave it on too long as it just spreads dissolved lacquer everywhere. Finish with Brasso for that deep, deep shine. If you are bothering to clean trim on a 21+-year old car you won't mind having to clean it every so often, will you? (It's now vulnerable to scratches and all sorts).
From here:
W123 Group on MSN
WARNING: Caustic soda causes burns. be careful. Wear rubber gloves, because you won't feel the pain until you rub your eyes.
To clean the aluminium trim blades - that become discoloured - running down the rear windows, you will need: a mild solution of sodium hydroxide (caustic soda), loads of cotton buds, paper towels, Brasso metal polish or similar, loads of time, and to realise that you are actually irreversibly damaging the trim, even if it does come up nice. The caustic soda dissolves the lacquer and de-anodises the aluminium, so you have to do it very slowly. Apply with cotton buds; you will see the liquid become frothy as the lacquer comes away and turns streaky, you need to use cotton buds to keep it under control. Wipe as you go and don't leave it on too long as it just spreads dissolved lacquer everywhere. Finish with Brasso for that deep, deep shine. If you are bothering to clean trim on a 21+-year old car you won't mind having to clean it every so often, will you? (It's now vulnerable to scratches and all sorts).