Be careful using a sub 1K stone to set a bevel, it will leave deep stria on the steel and that stria can cause micro chipping in the final finishing hones.
It is better to use a 1k to set the bevel and keep the sub 1k for edge correction, even then use very little pressure.
It is common to use too much pressure when we want to something done quickly to see results, as in a test.
Crumbling, micro chipping at the edge is what is common from rust.