That's not CoA, that's CoC ...
Here you can see how Koby loses consciousness.
What is not known is whether it is CoC coating because it is the pretimeskip.
And you can see how Shank's sword turns red when blocking an unnamed basic punch from the injured Akainu.
So despite the use of Shank's CoC or CoC coating, Akainu's magma was still able to affect the sword, which would indicate that Akainu's magma is more powerful than Shank's haki.