@ boldFirst of all, it was not melted instantly. It took more than 1 to 2 seconds. Second of all, that was a ribcage Susanoo made by a worn out kage summit Sasuke. The raikage's durability is somewhere inbetween a v3 and v4 Susanoo given how he tanked a FRS with little damage. Mei's boil release will take too long to melt his skin.It didn't barely burn through Sasuke's Susano'o. It was almost melted down in like 1-2 seconds. Sasuke survived only thanks to Zetsu.
Not to mention, Mei can easily alter the PH and density of her 'acidic particles' to much higher level, seen when she turned White Zetsu to blob in an instant with her concentrated Futton or when she melted Madara's V4 from quite a distance, before it even managed to hit her.
And what does FRS even have to do with Futton? FRS and Futton are completely different, since the first bases on pure sharpness and multiple micro-strikes, while the latter HAS CHAKRA-DESTRUCTIVE PROPERTIES. It doesn't matter what 3rd tanked - Futton thanks to its nature shits on any form of chakra shields and defenses.
@2nd bold
Scans where she melted his v4? I do hope you realise that Madara's v4 Susanoo is the one that withstood the impact of mokujin slamming a TBB into it's sword. Lol
OT: Raikage stomps. Mei's attacks will take far too long to do any actual damage, and the Raikage's pain tolerance and durability is massive. He tanks her attacks, and beats her down in CQC. This is not a competitive fight, but an absolute rout.