Copper-tin-(zinc) electrolytes as nickel-free alternatives
MIRALLOY® has been offering alternative nickel-free plating for fashion jewellery since 1981. With MIRALLOY®, electrolytes are used to deposit copper-tin or copper-tin(-zinc) coatings in rack and barrel plating. Depending on the electrolyte used, white or yellow layers can be deposited.
MIRALLOY® coatings stand out due to their excellent distribution of metal and, depending on the bath type, high tarnish resistance, levelling, abrasion resistance and exceptional corrosion resistance. A further plating layer with gold, rhodium, palladium or other precious metals, as well as tarnish protection if required, can be added with the right pre-treatment to create optimal corrosion protection.
Electrolyte characteristics
Electrolyte type Alkaline-cyanide
Metal content 10.5 g/l Cu 21.5 g/l Sn 1.6 g/l Zn
pH value Alkaline
Operating temperature 60 °C
Current density range 0.5 A/dm²
Plating speed Approx. 0.12 μm/ min at 0.5 A/dm²
Anode material MMO (type PLATINODE® 167)
Coating characteristics
Coating Copper-tin-zinc
Alloy composition 85 wt. % Cu 10 wt. % Sn 5 wt. % Zn
Colour of deposit 2 N
Brightness Bright
Hardness 400 HV
Max. coating thickness 20 μm
Density of the coating 8.4 g/cm³
Advantages
Copper-tin-(zinc) alloy coatings of white or yellow colour
Diamagnetic
Nickel-free (§27 of REACH, Ann. XVII, Reg. (EC) No 1907/2006, Standard 100 by OEKO-Tex®)
Resistant to tarnishing and corrosion
Excellent layer thickness distribution
Can be lacquered
Can be combined with precious metals
Tried and tested process does not cause allergic reactions in the way that nickel does
Applications
Costume jewellery
Ear studs / earrings
Necklaces
Bangles
Wrist watches
