C18200 VS C18150

What is the Difference between Class 2 Electrode Materials C18200 and C18150 (CuCr and CuCrZr)?


Short Answer:

·      Properties (mechanical, physical and electrical) of C18200 and C18150 are the same; both alloys meet required properties for Class 2 electrode material as specified by AWS J1.3/J1.3M:2020

·      C18150 contains a low-level addition of zirconium and is specified for welding galvanized and coated steel.

·      C18150 will meet composition requirements of C18200 when the chromium content is controlled and can be substituted for C18200.


Longer Answer:

C18200 CuCr - What Chromium does when alloyed with copper

·      Copper alloyed with about 1% chromium has been the standard spot-welding electrode material since the early 20th century and used since the 1930’s in automobile manufacturing.

·      Chromium (Cr) added to copper (Cu) provides the basis for copper to be hardened by heat treating, whereas most copper alloys harden by work hardening only.

·      A very small amount Chromium, less than 0.4 Wt.% is precipitated in the copper crystalline microstructure as extremely fine nano-sized particles that retards and limits slippage in the microstructure, effectively increasing the strength and hardness for the copper; aka, precipitation hardening.

·      Additionally, chromium precipitate in copper increases the softening temperature by limiting and decreasing the self-diffusion of copper at elevated temperatures that would normally result in softening via recrystallization, aka, softening resistance

During the 1980’s, galvanized steel (zinc coated) became a new standard in the automotive industry to provide increased corrosion resistance in automobiles. With increased usage of zinc coated steel, automobile assembly plants were experiencing spot welding issues with reduced electrode life and electrodes sticking to the work. The industry quickly learned that CuCr electrode material from Europe performed better than C18200 produced in the US. The difference was the addition of a very small amount of zirconium (Zr).


C18150 - What Zirconium does when added to C18200

·      The zinc from the galvanized coating coats the copper electrodes and alloys with the copper, forming a copper-zinc alloy (brass) at the electrode face that is now softer and results in accelerated mushrooming and wear of the electrode face. The addition of zirconium (Zr) to C18200 extends electrode life when welding galvanized steel by interfering with the alloying of zinc with the copper electrode face.

·      Zirconium reportedly improves creep strength of C18200 at elevated temperatures.

·      C18150 is specified for many high temperature applications outside the typical resistance welding markets because of the elevated temperature properties attributed to the Zr addition.


C18200 and C18150 have identical room temperature properties, i.e., hardness, electrical conductivity, tensile strength, and elongation, and are both suitable as RWMA Class 2 electrode materials as specified by AWS J1.3/J1.3M:2020

  • C18150 is specified for welding coated materials to improve electrode life.
  • C18150 is specified for nuclear and particle physics application components (ITER, tokamak, synchrotron light energy reactors).
  • C18150 is specified in aerospace applications for rocket engine components.
  •  C18150 and C18200 are specified for use in electric power generation and for rotor bars, end rings, and commutators in motors.
  •  C18150 and C18200 may be specified for electric connectors and contact applications.
  •  C18150 and C18200 may be specified as heat flux materials in many applications including casting molds for other metals.