This link can help you:

http://www.corrosion-doctors.org/Principles/Conversion.htm

Thanks Jose. Is there any derivative approach for this?

In this link

http://www.princetonappliedresearch.com/Literature/index.aspx

you can find an Application note " Basics of Corrosion Measurements" that can be useful to you.

There are a lot of books where you can find the derivation. I can give some reference if you need.

http://www.uobabylon.edu.iq/eprints/publication_12_18564_228.pdf

This a good book:

CORROSION ENGINEERING

Principles and Solved Problems

BRANKO N. POPOVELSEVIER

I'm skeptical of the attempt to convert between units that have no fundamental relationship.  Current density does not have any automatic relationship to penetration depth of a corrosion process.  You can make a number of assumptions to bridge this logical gap, but they are just that:  assumptions. 

When a metal corrodes, it does not usually do so uniformly across a given surface area.  Instead, there are areas of greater penetration (usually called pits), and lesser penetration.  In addition, there are passivation issues to be considered, and impurities in your metal substrate, both of which are usually the source of pitting behavior.  If you were to examine your corroded samples under proper microscopy, those pits would become readily apparent, particularly if the oxide layer is first carefully removed.

The point is that a given current density focused on a pit produces a very different result from one that is spread uniformly over a given surface area.  I very well know that there are various alleged conversions out there, all based on the assumption of non-pitting behavior, but none of them are capable of dealing with the varying passivation behavior introduced by the choice of electrolyte, nor with substrate impurities. 

And don't forget that atmospheric CO2 creates carbonate or bicarbonate (depending on pH of electrolyte) in your solutions during your experiment, which are themselves powerful passivators for Fe, Al, Mg, Zn, among other metals.  Thus, your conditions are changing, even as you make measurements.

So beware of using conventions that have serious flaws in their underlying assumptions.

i totally agree with with F. Louis Floyd.

You can calculate by equation as was supposed by Selvarani Ganesan.... but these values will be always just assumption. There exist too many factors which have influence on corrosion rate (structure of the material, stability passive layer if it exist,

aggressiveness of the environment ,it can also change during long period etc.) But for roughly estimate  it is acceptable for some way. It is necessary to add a safety factor

In my opinion, it is important to keep basic concepts clear.

The transformation of an electrical measurement (current) to mass loss (grams) is always valid in corrosion experiments. It corresponds simply to the application of Faraday’s law (96500 coulomb/equivalent).

Different aspect is the concept of active/geometrical surface with respect to which the measured current is normalised. Geometrical surface corresponds to the sample’s area wetted by the electrolyte. When the whole surface is also “active surface” (it is corroding uniformly) then conversion of current density to penetration depth is obtained straightforward through material’s density.

When the active surface is less than the geometrical surface then the so-called localised attack takes place and penetration depth can only be obtained (as above) if current is normalised with respect to the active surface.

Dear Anuruddha

    You have a current density and you need to convert it to corrosion rate. You can use the following formula:

CR= 0.00327 x (i corr) x (e/P)

CR: corrosion rate in mmly

i corr: corrosion current density in microamper/cm^2

e: equivalent weight of metal or alloy

P: density of metal or alloy

Best Regards

Rana Anaee

Dear Anuruddha

The attached link will help you to convert data between the most common corrosion units in usage especially what you asked about ; 

http://www.corrosion-doctors.org/Principles/Conversion.htm

Regards.

Alobaidi Haitham M.