Commercial welders use one very smart way to identify metals and this method is called spark check with a grinder. There are well organized spark charts in the text books and in various websites where the sparks from the test can be compared. Some commercial welders also use the magnet test and yet others use the puddle test with a TIG torch.

There are various factors that can affect the decision of the commercial welders when it comes to metals and especially when they have to perform TIG welding on cast iron metals. The main question here seems to be which is the right filler rod for the cast iron. The high nickel rods that are sometimes used comprise of nickel mainly and are expensive. The NI rods show great compatibility with TIG welding cast iron. The nickel rods are very good at that as the nickel absorbs the carbon and iron but is still ductile.

Commercial welders further say that nickel is similar to cast iron in regards with the thermal expansion. When the thermal cycles and the thermal expansion are ok, then the commercial welder can use an aluminum bronze filler rod. When the steel is mild, the commercial welder can use steel rods of 7018 and 6013, yet a carbon pickup will cause hardening of the weld deposit.

The aluminum bronze TIG rod can be utilized by using DCEN and AC welding currents, yet the aluminum bronze filer rod is quite sluggish on the DCEN. A current that is changing will provide cathotic etching which will break the surface oxides. For that reason AC is used by the commercial welders to TIG weld aluminum. Sometimes, small amounts of cleaning makes difference on the aluminum bronze filler rod. When AC is used, it is possible for the commercial welder to get a fluid puddle that wets out into the base metal and does not need a lot of amperage.