7.3.9 Copper Coatings
Even though copper is soft, it has many engineering applications in
addition to its decorative function.O ne such application is the corrosion
protection of steel. It can be used as an alternative to nickel to prevent
fretting and scaling corrosion. Copper can be electrochemically deposited
from variousa queous solutions. The properties of the depositw ill depend
on the chosen bath and the applied procedures. The hardness of the layers
varies from 40 to 160 HV.
Since copperi sv ery noble, it causes extreme galvanically inducedl ocal
corrosion of steel and aluminums ubstrates. Because of this,e xtreme care
must be takentop roduce well-adhering nonporous layers.
The corrosion protection provided by ac opperc oating is twofold,
consisting of an originalbarrier action of the coating layer and asecondary
barrier action of corrosionp roducts. The low EMF of copper is responsible
10
− 3
10
− 4
10 − 5
10 − 6
10 − 7
40
20
0
− 20
− 40
− 60 − 80 − 100
Corrosion potential, mV(vs SCE)
Bath: 0.1M NH 4 Cl
Area fraction copper
FIGURE 7.13
Data showing that the fractional exposed areao fc opper in copper/gold system is linearly
related to the corrosion potential at low-exposedc opper areas.
Coatings
433
CAT8247—CHAPTER 7—17/10/2006—15:02—TRGANESH—XMLM ODEL B–pp. 403–485
Even though copper is soft, it has many engineering applications in
addition to its decorative function.O ne such application is the corrosion
protection of steel. It can be used as an alternative to nickel to prevent
fretting and scaling corrosion. Copper can be electrochemically deposited
from variousa queous solutions. The properties of the depositw ill depend
on the chosen bath and the applied procedures. The hardness of the layers
varies from 40 to 160 HV.
Since copperi sv ery noble, it causes extreme galvanically inducedl ocal
corrosion of steel and aluminums ubstrates. Because of this,e xtreme care
must be takentop roduce well-adhering nonporous layers.
The corrosion protection provided by ac opperc oating is twofold,
consisting of an originalbarrier action of the coating layer and asecondary
barrier action of corrosionp roducts. The low EMF of copper is responsible
10
− 3
10
− 4
10 − 5
10 − 6
10 − 7
40
20
0
− 20
− 40
− 60 − 80 − 100
Corrosion potential, mV(vs SCE)
Bath: 0.1M NH 4 Cl
Area fraction copper
FIGURE 7.13
Data showing that the fractional exposed areao fc opper in copper/gold system is linearly
related to the corrosion potential at low-exposedc opper areas.
Coatings
433
CAT8247—CHAPTER 7—17/10/2006—15:02—TRGANESH—XMLM ODEL B–pp. 403–485