Stainless steel is a steel alloy containing chromium and nickel. Stainless steel is widely used in the medical profession to make pins and other parts that are implanted into the human body. Since it is non-reactive, it has no taste caused by electrolytic reactions and is considered a safe metal to be in contact with living tissue. Aluminum is not an inert metal. Chrome-plated bits are not reactive, as long as the plating is intact on the whole surface of the mouthpiece.
Plastic bits are now available.
Of course, no electrolytic reactions at all occur with plastic or rubber bits. Getting your horse or mule to salivate through electrolytic reaction does not guarantee that he will accept the bit. Bit acceptance ultimately comes through kind and patient training. As you teach and physically condition your equine, keeping him relaxed and calm, you'll find that he will quietly champ the bit and maintain a relaxed jaw. She has trained horses for 24 years, for the past 5 years focusing on mules and donkeys.