Litharge can be purchased at the ceramics store. Basic
Lead Carbonate is called White Lead and is used in paints
for boats. Lead hydroxide can be made from Lead Nitrate and Sodium hydroxide.
80 grams NaOH dissolved in water is added to 332 grams Lead Nitrate
dissolved in water and a white ppt immediately form's. This is lead Hydroxide
and it should be washed a number of times before it is added to the tank.
The
amount of compound to add to the tank depends on the amount of Lead Dioxide that
was deposited on the anode that was plated. The amount of compound to add to the tank depends on what
particular compound you are using and is thus:
| Compound | Grams of compound to add to tank per gram PbO2plated. |
| Litharge | 0.933 |
| Lead carbonate | 1.12 |
| Basic lead carbonate | 1.08 |
| Lead hydroxide | 1.01 |
If the tank becomes neutral before all of the amount of compound is added simply stop adding. Add some Nitric to put the pH low.
The following is some observations regarding the addition of compounds to
tank.
Lead carbonate PbCO3 (lab grade and dry from container) dissolves
easily with some bubbles, more bubbles and foaming if using surfactant.
Basic
lead carbonate (PbCO3)2:Pb(OH)2 (lab grade and dry from container) won't
dissolve easily and will float on top of the liquid and if the spoonful is large
enough to overcome the surface tension of the plating bath it will sink as a
fluffy lump and remain on the bottom where it will dissolve slowly with the
occasional big bubble of CO2 emitted. If using surfactant in the bath the basic
Lead Carbonate will 'wet' much easier and dissolve easily and cause a large
amount or rising foam which can be difficult to keep in the tank. The only way
to make this compound dissolve satisfactorily in a bath that has no surfactant is
to make a slurry of the compound before adding to cell. This is done by putting
some water and the basic Lead Carbonate into a (coffee) jar and shaking
vigorously until the powder wets. This slurry will dissolve instantaneously
without too much foaming. Add small amounts at a time.
Lead Hydroxide
dissolves easily and creates no bubbles.
Lead Oxide (PbO) Litharge. This
will dissolve easily if the particle size is small. If the Litharge is put into
a container and stirred, the particles that remain in suspension will dissolve
easily (because they are small). The larger particles will remain on bottom of
bath container for a time, this is no harm.
PbO is a good cheap neutralizer
and it can be added to tank so that there is always some of it on the bottom of
the tank where it can be stirred up now and again.
Ions that are bad news in a plating tank, according to the literature,
are:
Chloride, Cobalt, selenium, arsenic and Iron. The only ion that is likely to
effect you is Iron. If you are using 'crocodile' clamps made of steel to make
connections to an anode that is being plated, you must be careful that no
corrosion (it is very likely to form on the damp clamp) falls or gets into tank.
Better not to use Iron at all. Not too sure about SS but it has been in a
plating tank and had no corrosion or ill effects reported. Keep Gouging rods out of
the tank as them may contain Iron particles.
Nitrites are formed at the cathode as a side reaction and can build up
in the tank. The addition of Hydrogen Peroxide to the tank has been used to
counteract this problem. The build up of Nitrites lowers
current efficiency and will give bad coats of Lead Dioxide. Resting the tank for
a day or two after it has been neutralized will allow Nitrites to convert back
to Nitrates and allow the tank to plate at its best. Bubbling air through the tank will speed up the process. Careful of splashes/spray.