In message , doozer
writes
bof wrote:
In message , raden writes

Scale remover (available all over the place) is the correct tool for
the job. Why anyone would want to **** about pouring diet coke around
a bath is beyond me.
Hmm, don't know how the % of active chemicals compares in the two
but:
Tesco value cola 9.5p/litre
Viakal (limescale remover) £5.36/litre
that's knocking on 60x as expensive vol for vol, maybe I'll give the
cola a go.


The acids are different in the two, hydrochloric in Viakal

AIUI Viakal is a mix of Maleic and Sulphamic acids, hydrochloric is
common in brick cleaner.




and Phosphoric in cola. So it is comparing apples and oranges
somewhat. They have different "strengths" and therefore will differ in
their effectiveness at removing lime scale.

There are a number of reasons Viakal will probably be better than cola.

The acid in Viakal is much more concentrated. I would expect a pH of
probably 1 or maybe 2 where as cola would probably be more like 6
(maybe 5) since the pH scale is logarithmic this means that Viakal has
at worst (2 and 5) 1000 times more free ions and hence 1000 times more
limescale removing "strength".

The fizzing of the limescale (and perhaps you bath enamel) is the acid
attacking it. The reaction is:

2HCl + CaCO3 -- CaCl2 + H20 + CO2

The resulting salt when using Viakal is CaCl2 which is very soluble in
water and therefore easily washes away. CaPO4 (Calcium Phosphate) which
is the result of using cola is not as soluble and therefore not so
easily removed.

--
bof at bof dot me dot uk