I've used citric acid before, with reasonable success - it's readily obtained in powder form for de-scaling kettles etc.
Perhaps slower, but a lot less nasty than oxalic.
As some trace will inevitably remain after flushing, it may be wise to neutralise it with an alkaline rinse.
Nowadays I'd be inclined to use a professional service, such as Lenton suggested above.
Perhaps slower, but a lot less nasty than oxalic.
As some trace will inevitably remain after flushing, it may be wise to neutralise it with an alkaline rinse.
Nowadays I'd be inclined to use a professional service, such as Lenton suggested above.