Steve Firth wrote:
zaax wrote:

On 4 Oct, 00:14, Andy Hall wrote:
On 2007-10-03 23:58:43 +0100, (Steve Firth) said:

The Medway Handyman wrote:
Oxalic acid wash. Some descalers are based on oxalic acid.
I'm not aware of any descalers that use oxalic acid. Oxalic acid is
toxic and descalers are frequently used on potable water supplies.
If not phosphoric acid - Lime Lite, but try a small area first.
Lime Lite is sulphamic acid, not phosphoric.
Sulphamic acid is the acid used in the majority of proprietary
descalers. It's non-toxic, a relatively mild acid and it's easy to make
up from crystals and near-impossible to create too strong a solution
because of its relatively low solubility compared to aggressive acids.
and IIRC, Fernox descaler is a fairly inexpensive way to buy it
reasonably easily.
patio cleaner?

That's usually hydrochloric acid.

Don't that on my paintwork ;(