Hydrogen Peroxide H2O2 Pickle
by Bill Seeley
Following is a paper on a special pickle I developed while attending graduate
school at the University of Kansas. I had designed and constructed a
rather complicated brass neck piece with many hard edges. After the
construction was completed the piece was pickled by the ordinary means.
This removed the black oxides from soldering, but there remained a though
red oxide coating. Removal by abrasion would have destroyed the hard edged
design. I had earlier come across a paper on a commercial pickling
formulation using hydrogen peroxide. From this formula I sort of reverse
engineered the following process. It is relatively safe, because it is
based on drugstore variety hydrogen peroxide.
There are no warranties. If you use this formulation you do so at your
risk. You may copy and share this paper. Please do not charge money for
it in excess of the copying cost.
Heat-treating and soldering of copper and copper based alloys can often
coat the metals with a combination of black (cupric) and red (cuprous)
oxide. The black oxide is easily removed in a standard warm sulfuric acid
or Sparex bath. This will leave a red smut, which, with other undissolved
oxides, forms a red oxide scale. This scale readily oxidizes further,
leaving a dark, nonuniform patina. It can be imbedded in the metal during
subsequent forging and drawing, so it should be removed. Abrasive removal
of the oxides can result in loss of design details and crisp edges. This
simple chemical treatment is offered as an alternate method for its
Hydrogen peroxide (H2O2 ) pickle eliminates the need
for abrasives, and has
the added attraction of being relatively inoffensive. The following
procedures and formulas provide for the removal of red scale from copper,
brass, bronze, nickel silver, reticulation silver and some gold alloys. It
will remove the copper coating from silver that has been accidentally
pickled in an iron contaminated acid. Curiously, it will also remove the
natural oxide layer found on aluminum. There is a great deal of latitude
in the formulas and a variety of surface finishes and textures can be
It is suggested that you run some tests before applying these formulas to
your work. Find the procedure that best fits your needs. When working
with any acid the possibility of damaging your work always exists. These
formulas can dissolve a brass piece and leave the silver solder seams
Some points to remember when using hydrogen peroxide pickles:
- Adding more acid to the solution will not improve its action. The
is just a catalyst or starter.
- Iron and silver will tend to shorten the life of the bath. This does
not mean you cannot put these metals in the bath.
- Use only sulfuric acid, Sparex or vinegar as the catalyst in these
- Use 3% hydrogen peroxide available in drug stores, or mix a 2-3%
solution from distilled water and concentrated H2O2
available through a chemical supply house. More concentrated pickles (5%)
can be mixed when deep, fast etching is desired. (Warning!
acid is very dangerous. Do not attempt without proper training and
Always add acid to water!
- Use these solutions warm(110°F), or about the temperature of a
bath. The hotter the pickle; the faster and coarser the etch.
The following formulas can be made up as needed, or they can be premixed
and kept for an extended time in the original brown bottle. It can be
reused until saturated (blue) and it stops working. Hydrogen peroxide
decomposes rapidly when exposed to light. The active life of these pickles
is limited to about four exposed hours. Put your solution back in the
brown bottle for storage.
The acid component of these solutions can be either measured or slowly
added until bubbles begin to appear on a sample of the metal. This signals
that the solution is active.
2 parts Hydrogen Peroxide (3%).
1 part water.
2-4% fresh sulfuric acid (5-10%) or Sparex solution.
1/2 cup Hydrogen Peroxide (3%).
1 Tablespoon fresh sulfuric acid (5-10%) or Sparex solution.
- Prepickle the piece in standard Sparex or sulfuric acid solution
(5-10%) and rinse. All the black oxides should be removed.
hot water to keep it warm. If possible suspend the piece in the warm
pickle. After a moment bubbles should appear on the piece. Agitate or
brush with a feather to clear the bubbles. Remove the piece from the bath
every couple of minutes to check the progress. It may take 5-10 minutes.
- Use a stiff tooth brush or brass brush to remove residue and rinse
- Pickle again in standard Sparex or sulfuric acid solution (5-10%)
to remove any remaining smut.
- Repeat steps #2, #3 and #4 if necessary.
3 parts Hydrogen Peroxide (3%).
1 part white vinegar (5%).
Follow the steps listed for solutions #1 and #2. When the metal emerges from
the pickle, it will be coated with a thick brownish green smut. This will
flash off when dipped in undiluted white vinegar.
These solutions can also be applied to warm metal with a brush and worked
into hard to get corners and intricate designs.
Long term exposure to these pickles can cause the copper to be dissolved
out of an alloy's surface. Brass, for instance, can be pickled until it
turns bright yellow. Even the mildest of the vinegar solutions can deeply
etch if left unattended. A deep etch will often reveal the underlying
crystal structure of the metal. Care should be taken and the process
As is the case with all corrosive solutions, these formulas should be
handled with care and in good ventilation
Hydrogen Peroxide pickle does not remove firescale from sterling silver.