Aluminum requires pure tungsten don’t worry about sharpening it if you preheat the aluminum it will weld betterIn the little experience I’ve had tiggin aluminum, it’s a slower weld. That aluminum will take a bunch of heat. You gotta fire up and let it soak before you start stacking them dimes. Steel wants to get hot in one spot and try to burn through with too much heat. You need more heat with aluminum cuz it disperses the heat much quicker through the entire workpiece. That’s just what it seems like to me.