SC13c Electroplating Flashcards
electroplating?
coats the surface of one metal with a thin layer of another metal
why electroplate metals? 2
~cost - silver and gold are expensive metals so can be electroplated on cheaper metals to make silver or gold plated jewellery
~resistance to corrosion - chromium doesn’t corrode so so objects such as steal parts can be electroplated with it so it wont rust
examples of electroplating?
gold may be electroplated onto cables to stop them from tarnishing
to electroplate you need:
~an anode (positive charge) made from plating metal
~an electrolyte, solution containing ions of the plating metal
~a cathode (negative charge) which is the metal object to be plated
electroplating silver onto a copper ring
~A direct current flows through the electrodes and electrolyte.
~Silver ions in the electrolyte move to the negatively charged copper ring.
~They gain electrons and are deposited as silver atoms.
~At the silver anode, silver atoms lose electrons to become silver ions, which go into the electrolyte.
~The longer the current flows, the thicker the silver layer on the ring becomes
half equations for when copper is electroplated with silver
oxidation - silver anode
Ag → Ag⁺ + e⁻
reduction - copper cathode
Ag⁺ + e⁻ → Ag
~the cathode is the electrode that gets coated with the metal
galvanising?
iron and steel objects can be protected from rusting by coating them with zinc
what does the thin layer of zinc on iron and steel objects do? 2
~improves corrosion resistance by stopping the water reaching the iron or steel
~acts as sacrificial protection and works even is zinc layer is damaged
how can galvanising be done? 2
~electroplating
~dipping object in molten zinc
how are food cans protected from rusting?
the steel is electroplated with tin which does not react with air or water
what happens f the tin layer on cans is damaged?
the steel can will rust faster as iron is more reactive than tin so it acts as a sacrificial metal to protect the tin
