Hello again medicinehawk, I would tend to say yes, in an instance such as that, the welder has done the same thing to the stainless weld and haz zone that would occur due to excessive penetration through the joint without proper backing and caused a condition that many refer to as sugaring. Simply put, stainless oxides do not posess the same characteristics as properly welded stainless, the black color would definitely indicate a level of oxide that would not be good. The stainless would likely lose it's strength as well as many of it's corrosion resistance and wear resistance qualities. I have to cut this short right now, I'll see if I can expand on this further, later. Regards, aevald
Had to take care of a few things, back now. Stainless is one of many materials that are very heat and environmentally sensitive to welding processes. Incorrect filler material match and you can have a number of issues come up that will effect the soundness of the weld, strength, corrosion resistance, errosion resistance, heat resistance, to name just a few. Contaminants that are present in the welding environment can also have an adverse effect on the soundness of the weld, this could be in the form of chemicals, incorrect shielding gas, improper use of shielding gas, even oils from the skin(handling the filler rod with your bare hands) can cause issues with achieving a sound weld in some extreme cases of welding application. When I look at a completed weld on most stainless steels I don't want to see any black or gray, along with the color, I look very carefully at the surface condition of the fiinished weld, if it is smooth and doesn't exihibit any rough, scaly, or porous surface texture but still has the black or gray color you are probably marginal on whether it can be counted on to perform as it should(even in this case I would not accept this condition). If it is rough, scaly, and you can possibly also see some porosity and has the black or gray color as well I would feel that the weld will definitely fail and not work as intended. Many welds that are done on stainless require full penetration welding from one side only, in these cases, either a backing gas should be used or in some cases there are products such as solar flux which can be applied to the back side of the weld joint to achieve this protection. When I am welding on T-joints and trying to minimize the discoloration or oxidation on the backside of the weld I will clamp a piece of aluminum angle iron on the side opposite of the one that I am welding to help with this, it will also act as a heatsink and in some cases this will also minimize distortion issues. Hope this is some of what you were looking for. Allan