Dear Rajininkanth,

As this steel is an alloy of iron and silicon you can use silicon preferential etching to delineate the defects at the surface layer of the material. For the composition of the preferential ething solution please follow the link: http://studentsrepo.um.edu.my/2316/6/BAB_3.pdf, Narurally you can control the etch composition to increase the etching rates at the defects.

You can find other preferential etching solutions by searching the web.

Best wishes

(30%)Ferric chloride solution helps a bit but unable to avoid pitting.