Frequently Asked Questions about Welding

Q: What do the different color codes on tungsten electrodes really mean? I know red is 2% thorium and green is pure tungsten (who doesn't?) but what do the other colors stand for? I can't find a straight answer anywhere.

A: There's a lot of conflicting information out there. The following is my best information, with references:

               |         AWS A5.12            |        ISO 6848
               |------------------------------|--------------------------
Oxide additive | type      color   percent    | type    color   percent
---------------|------------------------------|--------------------------
(pure W)       | EWP       green   -          | W       green   -
ThO2           | EWTh-1    yellow  0.80-1.20  | WT10    yellow  0.80-1.20
ThO2           | EWTh-2    red     1.70-2.20  | WT20    red     1.70-2.20
ZrO2           | EWZr-1    brown   0.15-0.40  | WZ3     brown   0.15-0.50
ZrO2           | -         -       -          | WZ8     white   0.70-0.90
La2O3          | EWLa-1    black   0.80-1.20* | WL10    black   0.90-1.20
La2O3          | EWLa-1.5  gold    1.30-1.70  | -       -       -
La2O3          | EWLa-2    blue    1.80-2.20  | -       -       -
CeO2           | EWCe-2    orange  1.80-2.20  | WC20    grey    1.80-2.20
specify**      | -         grey    -          | -       -       -

*Miller Electric's GTAW manual, which ostensibly lists the AWS classification of different electrodes, shows a percentage range of 0.90-1.20% for EWLa-1 tungstens.

**According to the Miller Electric GTAW manual, the AWS classifies grey electrodes as containing "other rare earths or a combination of oxides."

Sources:

• Intercon Enterprises, Inc.
  
• Gas Tungsten Arc Welding published by Miller Electric Mfg. Co.
  
• Color codes listed above are consistent with my own experience purchasing or examining packages of new EWP, EWTh-1, EWTh-2, EWZr-1, EWLa-1.5 and EWCe-2 electrodes. I have not personally seen EWLa-1, EWLa-2, or grey-coded electrodes.
• PROFAX/LENCO agrees with the above listing for black-coded tungstens.
• Welding-direct.com used to claim that black-coded tungstens contained 1.5% lanthanum oxide. Now they list them as 1%.

Dissenting Sources:

• Welding Nozzle International claims that black-coded tungstens contain 2% lanthanum oxide. This is contradicted by my references.