Thermocouples, you mean to extend the wiring length?
That adds new Seebeck effects to the wiring and can disturb the specified delta V per °C rating.
I suppose if you need to do a fair amount of ' low temp' Aluminium to other metal soldering it may be worthwhile to make a CO2 filled box using dry ice and burn out any remaining O2 with a candle flame. Then work gently to as not disturb the trapped CO2 layer and mix air in when cleaning and soldering the aluminium.
A good liquid cleaner for the Aluminium oxide is some lye solution. But you'd need to have that in the CO2 box, so u dip the pre twisted wires being joined, let the oxide get chemically stripped and then solder with no O2 exposure. No scraping.