Homebrew PCBs

@markus:

i think your pump principle is like those medical "silicon hose rotrary 
pumps".
they are used for pumping blood and other liquids.
the advantage is the silicone hose can be replaced easily, making 
sterilization
unneccesary, the expensive pump motor, casing etc. is reused...

i have no idea where a rc plane builder may need such a pump (i'm kind of 
involved
in that now...). maybe for tank refueling on glow engine planes (i only use 
electric power).

but i think this is not a pump for spray etching, it it a slow pump.


what pump i suggest:

it is not too hard to build a centrifugal pump.
you can look for small aquarium pumps too.
if you get a EHEIM pump (look at pc watercooling supplys)
you may isolate the permanent magnet with thick laquer and that's it.
it uses ceramic shaft, all other things are plastic i think (only the 
permanent magnet rotor not).

these are very good pumps and i think they would be well suited.
(the winding is totally encased in plastic)
(i cool my pc with it, so i know it... you can't hear these pumps from 1 
meter away...)

another option is to build the pump immersed in the etchant.
the shaft goues up to the top and there is a motor mounted.
use a plastic shaft or a (expensive) metal which is not etched.

would be very easy to build from a small centrifugal pump where you simply 
take the motor out.

do not try to use any commercial pump which uses some kind of sealing like 
a stuffing box.
the etchant will get through and corrode the motor.

the centrifugal pump is not very critical design, only needs a balanced 
rotor.
(easiest is taking one from another pump).
piston pumps are difficult to keep sealed, with metal in the etchant.

st