Australia's Science Forum

I have been asked to clean soft copper pieces that have been used for heating. I am hoping there is an easier way to do this than with steel wool and lots of manual scrubbing. Some pieces are coming up okay with minimal fuss but some are extremely hard to clean. Any suggestions?

Nitric acid will do the trick. Soak briefly and rinse using forceps.

If you use this method, make sure its done in fume cupboard. Copper with acid nitric will produce dense brown fumes.
L

Coke & alfoil. Soak them in coke and leave for a while. Rub with foil, then rinse.

I would not use Nitric acid, Nitrogen Dioxide has an EXTREME hazard warning on Chemwatch.
I was once accidentally exposed to this in my early days as a labbie tipping an unmarked beaker of clear solution down a sink that had small bits of copper in the bottom. There was this puff of brown gas that smelt and caused me to cough irritatedly for the rest of the day.
I notified the front office but suffered not long term effects.'
I have since been very way of coper and Nitric acid.

Reading down the SDS you find it is an EXTREMELY poisonous, corrosive and oxiding gas.
It can produce chemical burns on contact with skin.
It wil produce chemical damage of the lungs after a single exposure, this may not manifest until sometime later.
It can cause severe irritation and burns of eyes skin and mucuos membrane

Copied from a sds
INHALATION: Exposure to Nitrogen Dioxide gas in low concentrations
produces an irritating effect on the mucous membranes of the eyes,
nose, throat, and lungs. Acute exposure through inhalation may result
in dryness and irritation of the nose and throat, choking, coughing, and
bronchospasm. Severe overexposure may cause death through
systemic, delayed pulmonary edema. High concentrations of
Nitrogen Dioxide gas may cause an oxygen deficient atmosphere.
Exposure to high concentrations may cause unconsciousness, and
under some circumstances, death. Typical symptoms of
overexposure are:
CONCENTRATION SYMPTOMS of OVEREXPOSURE
25 ppm: Delayed (5-72 hours) pulmonary irritation
after 8 hour exposure.
100 - 150 ppm: Delayed (5-48 hours) pulmonary edema
after exposure for 30 - 60 minutes.
200 - 700 ppm: Delayed (5-8 hours) severe pulmonary
damage after only a few breaths.
After inhalation of a few breaths of Nitrogen Dioxide, there is no
immediate reaction, or only a very slight respiratory discomfort,
headache, dizziness, or lassitude. After 5-8 hours (frequently after
the employee has left the workplace and returned home), it is noticed
that the victim’s lips and ears have a blue (cyanotic) color. There then
follows rapidly increasing symptoms of breathing difficulty, irregular
respiration, choking, dizziness, headache, increasing cyanosis,
tightness in the chest, nausea, vomiting, lassitude, and palpitations. Left untreated, death frequently occurs. Physical
examination immediately following overexposure reveals an accelerated respiratory rate, decreased vital capacity,
generally suppressed breathing sounds, low blood pressure, and a platelet count elevated by 10-100%.
SKIN and EYE CONTACT: Prolonged exposure may cause potentially harmful amounts of Nitrogen Dioxide to enter the
body via absorption through the skin. The gas may be irritating to the skin, especially in a moist environment, for prolonged
periods. Symptoms of skin overexposure may include scratchiness, pain, and redness. If Nitrogen Dioxide contaminates
the eyes, severe injury and swelling of the eye tissue may occur. Contact with rapidly expanding gases (which are released
under high pressure) may cause frostbite. Symptoms of frostbite include change in skin color to white or grayish-yellow.
The pain after such contact can quickly subside.
OTHER POTENTIAL HEALTH EFFECTS: While ingestion is highly unlikely, ingestion of Nitrogen Dioxide can damage
the tissues of the mouth, throat, esophagus, and other tissues of the digestive system. Ingestion of Nitrogen Dioxide
can be fatal. Additionally, aspiration by inhalation is possible, causing pulmonary edema or death.
HEALTH EFFECTS OR RISKS FROM EXPOSURE: An Explanation in Lay Terms. Overexposure to Nitrogen Dioxide
may cause the following health effects:
ACUTE: This gas is toxic and damaging to the respiratory system, as well as contaminated skin and eyes. Overexposures
can result in severe irritation and burns of eyes, skin, mucous membranes, and any other exposed tissue. If inhaled,
delayed pulmonary damage and breathing difficulty may occur. Overexposure to this gas may be fatal. Contact with
rapidly expanding gases may cause frostbite.
CHRONIC: Prolonged or repeated overexposures may cause respiratory problems, bronchitis, hacking cough, nasal
irritation and discharge, increased fatigue, and alteration in the senses of taste and smell. Repeated overexposures to
Nitrogen Dioxide can also result in dental erosion and gum disorders.HEALTH

Salt and vinegar?

Try sandpaper or wet/dry sandpaper. You still have to do the manual scrub but it is softer on the fingers than steel wool.

Question: how soft is soft copper? Are you using copper foil or are you using the heavier copper sheet?

I use (rightly or wrongly) about 1M hydrochloric acid. Soak for a short time - usually electrodes - then rub if necessary with a scourer and rinse.

ahh good ol nitric acid! In my days in industry[ smelter] we used this by the bucket load. I used to have brown fingers and nails all the time and people thought I was a smoker!
These were the old days when safety was not as strict and good as it is now.
We didn't use gloves - except when using HF acid, we would pick up hot beakers from the big hotplates with our fingers - yes calluses on them. we would reach over with no gloves on and swirl beakers on the hotplates - which held maybe 100 beakers at a time, so it was a production line, swirling each beaker a few times while they boiled.
I did testing on galvanised coating on roof nails for customer service, weighing each nail, dipping in conc Nitric, wiping that off the nail then re-weighing.. in a fume cupboard??? no way!
I did creek samples, and one was extracting selenium into toluene. I would have a big bench in the middle of the room covered with hundreds of little beakers all with toluene waiting to go through an AAS.. and no fume hood over the bench - boy did I get high on those weeks
I would pipette blood and urine by mouth! pre-Aids days guys, but a little clot in the pipette and you tasted it... yuk.. the days of Ford Pills where urines were green..
ah those were fun days.. and I still wonder if it will all catch up with me and who do I chase for compo if that happens

Gosh with all that going through your system, no self respecting bug would have survived there. You are no doubt well pickled and will survive to eternity.

You need a medal Sunray, it when you think back is scary, that is for sure.

Sunray,
where did you work? I worked at electrolytic refining and smelting in Port Kembla.
Using heaps of HNO3 and copper shavings. I worked in QC lab.
L

I'd try HCl, dilute. A lot of chemistry is reactions that in the real world would be considered foolhardy. We used to make Nitric Dioxide near an open window and issue a warning , now it gets done in the fume cupboard.