开云体育I'm not sure what initial concentration of phosphoric acid (PA) you are starting with, Brian.
I bought some a while back (in NZ) from a chemical supplier (I think) at the strongest
possible solution, namely 85%, at which level it is a fairly dense and syrupy liquid. I think it is
also commercially available and possibly cheaper at 70%, and also in various proprietary
products at lower concentrations which are designed to be used without further dilution.
I've just done a bit of further research, which suggests to me that the solution for rust
conversion (rather than removal) is in the 20-30% ball park. That is also probably about right
for soldering flux, although I don't think the exact concentration is crucial. I'd therefore agree
with your recommendation to add two parts of water to one of PA, provided that the starting
point is 70% or 85%
PA at low concentrations is not harmful to humans - indeed it is a constituent of many drinks
(especially Coca Cola) and some processed foods, in "food safe" form, which means free of
impurities. The significance here is that it is quite safe to clean drinking vessels with PA
followed by simple rinsing.
The 85% is highly corrosive to skin and membranes. If diluting this or the 70% variety, the
acid should always be added to water (as with sulphuric and other "strong" acids), and even
then some eye protection is desirable imo.
Getting back to the original topic (connecting rods), the effect of PA if properly used is to
convert some of the surface iron or iron oxide to iron phosphate, which has a grey patina.
This is not bright like s/s, but does look metallic, and it serves to protect the underlying metal
from re-rusting. I haven't actually done this, but I think it might be the way to go.
Bruce Cropper
On 11 Oct 2021 at 11:24, Brian wrote:
>
> Paul, I know Bunning's sell it here in Oz, but basically you need to get yourself
> some rust converter which is phosphoric acid wash the steel bits in it and then
> wash in the white spirit and dry in a oven before coating.
> Another advantage of buying some phosphoric acid is that you can mix it at a 2:1
> ratio 2 parts water and 1 part acid and you have the perfect flux for soldering. > ------ Original Message ------
> From: "Paul Holmes" <heatonwood@...>
> To: [email protected]
> Sent: 11/10/2021 9:06:33 PM
> Subject: Re: [o14] Slaters Lyn
>
>???? Here is the rather nice 14mm gauge axle?
>
>
>
> Virus-free. www.avg.com
>
>
>
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