Hi Anindya,
Friction coefficient is directly dependent on surface conditions.
As you mentioned the value 0.57 might be value under Lab test condition. It need to be investigated what is the surface roughness value of those Steel plates.
The universally accepted value 0.3 is for structural steel to structural steel friction
and without corrosion or rusting (i.e. new steel members).
I would recommend to use 0.5 value at the corrosive atmosphere e.g. at seashore and where
operating cycles are frequent e.g. Adsorbers of PSA.