The chart has aluminum and SS as compatible(green) . We used a ton of SS bolts at work (retired engineer) and we often used dissimilar metal nuts with SS bolts. SS nuts and bolts have a nasty propensity to gall when you tighten them then you can never get them off without cutting them or breaking them off. That's pretty darn hard with a 5/8" or 3/4" bolt. I'm guessing that is why they used different metals for the nut and bolt.We installed a Kohler one-piece toilet in 2013. The 'Quiet Close' lid failed so I tried to remove the lid bolts. No go on one of them; the bolt was frozen. I finally removed it and found that the anchor nut is made of aluminum, and the bolt of stainless steel. This is very basic design flaw! Aluminum fasteners should NEVER be used with steel or SS due to bimetallic / galvanic corrosion, which will cause the bolt to freeze on the nut. I managed to separate them and found clear evidence of bimetallic corrosion. I sent a complaint to Kohler USA; it will be interesting to see if and how they respond. Attached is a photo of the frozen bolt after it was removed. You can see the green annodized anchor which broke -- and the SS bolt. Also attached is a metal chart that I sent to Kohler which shows compatible metals in green -- and pairs that will cause corrosion in red. This is engineering 101 stuff.