Tarnish
Removal
By: Bridget Thai
(Zharina, 2003)
What is Tarnish?
- chemical reaction between metal and nonmetal
- results in metal oxide or metal sulfide
- corrosion formed on the surface of metals to preserve the layers below
- formed on metals like silver, copper, brass, etc.
(Murphy, 2012)
(Brian, 2005)
(Ankersmit, 2012)
Silver Tarnish
Formation of silver sulfide
("Hi-Res Images of Silver", n.d.)
-
also known as silver sulfide
- occurs when silver metal reacts with hydrogen sulfide in the air or with materials containing sulfur
- black solid
- insoluble in all solvents
Physical Removal
- scrub the tarnished metal with an abrasive
- some metal layers underneath also removed
Chemical Removal
(A.M.F., 2006)
- chemical solutions
- electrochemical cleaning
- galvanic cleaning
Galvanic Cleaning of Silver Tarnish
- connect tarnished metal to aluminum sheet
- aluminum acts as the reducing agent
- submerge both in a sodium bicarbonate electrolyte solution
- sulfur transferred from silver to aluminum via electrolyte
- aluminum has larger affinity to sulfur than silver
- produces silver, aluminum sulfide, hydrogen gas, and hydrogen sulfide gas
Optimizing the Reaction
- Heating the electrolyte increases the chances for successful collisions between the particles
- should not be heated to the point where the electrodes melt
- Smaller objects or objects with many creases will react faster due to increase of surface area
- The addition of a catalyst will speed up the reaction process
Effects on Society
("At the Repair Bench , 2009)
-
Tarnish removal is used for vanity purposes rather than practicality
-
Popular use of tarnish removal process is the cleaning of jewellery
- silver plated jewellery can be cleaned without removing the coating
Effects on Industry
("Parliament Buildings", 2008)
- tarnish is useful for preserving metals such as statues and copper roofing, so removing tarnish is not really sought out
-
used to preserve stored metals
Effects on Environment & Human Health
-
hydrogen sulfide released from galvanic reaction is poisonous if inhaled at large quantities (also smells bad)
("Tarn-X", n.d.)
- many tarnish removers are corrosive to skin and toxic if ingested
- if incorrectly disposed, harmful to environment
- gets into water supply
-
newer tarnish removing products aiming at being non-toxic and safer for environment
Electrochemical Cleaning of Artificially Tarnished Silver
J. Novakovic, P. Vassiliou, E. Georgiza
- conducted at School of Chemical Engineering, National Technical University of Athens
- Silver tarnished with chlorine and sulfur was observed when added to a galvanic cell with aluminum and sodium carbonate
- found that after an hour, small samples of sulfur and chlorine were still present on the silver
Which of these metals do not tarnish?
(Nelson, 2013)
a) silver
b) gold
c) copper
d) brass
In what ways is tarnish useful?
c) it helps break down metals
d) none of the above
a) it acts like a shield for rest of the metal
b) it is not useful
A
What are two common elements that cause tarnishing?
C
a) oxygen and chlorine
b) oxygen and hydrogen
c) oxygen and sulfur
d) none of the above
What does hydrogen sulfide smell like?
(Clark, 2013)
a) cheese
b) almonds
c) rotten fruit
d) rotten eggs
47 Ag Silver. (2010). Retrieved January 8 from http://images-of-elements.com/silver.phpZharina, E. (2003). Clean Tarnished Silver Jewellery. Retrieved January 8, 2014 from http://jewelrymakingjournal.com/clean-tarnished-silver-jewelry/A.M.F. Supplies. (2006). Products. Retrieved January 8, 2014 from http://www.amfsupplies.com/products.htm
Brian. (2005). Tone down that brass for summer runs!. Retrieved January 6, 2014 from http://steelheadnotebook.net/forum/index.php/topic,542.0.html
Canadian Centre for Occupational Health and Safety. (2012). Hydrogen Sulfide. Retrieved January 8, 2014 from http://www.ccohs.ca/products/databases/samples/cheminfo.html
Canadian Conservation Institute. (2013). Recognizing Metals and their Corrosion Products. Retrieved January 6, 2014 from http://www.cci-icc.gc.ca/caringfor-prendresoindes/articles/metals-metaux/index-eng.aspx
Clark, C.(2013). “What is that rotten egg smell?” Emergency Light Batteries. Retrieved January 8, 2014 from http://www.lightingservicesinc.net/life-safety-blog/?BBPage=1
Cleaning Your Silver. (n.d.) Retrieved January 8, 2014 from http://www.darylscience.com/Demos/Silver.html
CUPE. (2011). Hydrogen Sulfide. Retrieved January 8, 2014 from http://cupe.ca/health-and-safety/Hydrogen_Sulfide
Di Giuseppe, M., Salciccioli, K., Harberer, S., Sanader, M.,& Vavitsas, A.(2012). Nelson Chemistry 12: University Preparation. Ontario Edition. Toronto, ON:Thomson Nelson.
Gagnon, S. (n.d.). The Element Silver. Retrieved January 8, 2014 from http://education.jlab.org/itselemental/ele047.html
Georgiza, E., Novakovic, J., Vassiliou, P. (2013). Electrochemical Cleaning of Artificially Tarnished Silver. 7223 - 7232. Retrieved from http://www.electrochemsci.org/papers/vol8/80507223.pdf
How to Clean Tarnished Silver. (n.d.) Retrieved January 9, 2014 from http://www.videojug.com/film/how-to-clean-tarnished-silver
Lenntech. (2014). Alluminium - Al. Retrieved January 8, 2014 from http://www.lenntech.com/periodic/elements/al.htm
Lide, D. R. (2008). Handbook of Chemistry and Physics, 89th Edition.
Murphy, E. (2012). Copper Cleaning. Retrieved January 6, 2014 from http://americanhomestead.blogspot.ca/2012/01/copper-cleaning.html
Parliament Buildings. (2008). Retreived January 8, 2014 from http://www.parl.gc.ca/About/Parliament/Education/CanadianSymbols/centre-e.asp
Silver Tarnish And Removing Tarnish From Silver Jewelry. (2005). Retrieved January 6, 2014 from http://www.newsletter.kaijewels.com/silver-tarnish.htm
Winter, M. (2012). Silver compounds: disilver sulphide. Retrieved January 8, 2014 from http://www.webelements.com/compounds/silver/disilver_sulphide.html
Tarnish Removal
By Cora
