According to my experience, Cr is very active, which can be oxidized immediately once contacting with air. Chromium oxide even cannot be removed by chromium etchant at room temperature. A method to remove the oxide layer I could come up with is using plasma bombardment. For example, while you are sputtering Pd, you can apply a high power to "dry etch" your sample surface before sputtering Pd. It would slightly help but not so sure if it can remove oxide layer completely or how long it would take. 

I would agree with Gary in principle. Clean the Cr by some means in the same vacuum in which you will later deposit the Pd. You may also try to heat it in pure hydrogen (must be flowing to remove the water from furnace) atmosphere as this would reduce the Cr atoms in oxides back to metallic state. Then you would need to introduce Pd without opening the whichever apparatus you would be using. But then we are talking all about almost atomic purity on the surface...  Is that really so critical?..  What if you nicely polish you chromium coating, apply Pd and anneal so they mix a bit by diffusion?..  you may still have pure Pd on surface and achieve solid bonding with the Cr sublayer. Palladium dissolves a lot of chromium so it should be possible. there is even eutectic so you could make it a TLP bonding technique. Of course  I don't know the thickness of your coatings, so you must take this into account in respect how much "bulk" you actually have at hand...

Dear Sahib,

You mean for sure a galvanic process and no PVD. Cr2O3 dissolves well in hydrochloric acid, but purified metallic chromium reacts very intensively with hydrochloric acid (do not take too long). However, in the air, chromium oxide immediately reappears and you do not get a metallic surface when changing the pickling bath in electroplating bath. If electroplating with palladium is carried out in an acidic bath with palladium chloride, it may be possible to remove chromium oxide directly in the electroplating bath by briefly switching the poles before electroplating.

Dear all i definitely gonna try your recommended techniques, please can you suggest me any literature about it so that i could polish myself more about it, thanks

The following ‘chrome etch’ was reported effective for Cr/Cr2O3 thin films: 2NH4NO3·Ce(NO3)3·4H2O (1 g) + conc. HNO3 (10 mL) + H2O (100 mL). To improve its selectivity for etching the oxide, I would suggest to immerse in this electrolyte solution ― preferably at uniform distance from the chromium (oxidized) surface to be etched ― a second plate of either aluminium or zinc, connected (wired) for direct electrical contact with the former chromium surface. Both these metals are more electropositive than chromium. It may help to add about 5 g of either AlCl3 or ZnCl2 to the former electrolyte formulation, depending on the selected metal being Al or Zn, respectively. This sets up a galvanic cell which generates a small current that enhances the electrolyte ability for removing the chromium oxide layer, due to the concomitant reducing action of the H+/H2 redox couple at the oxidized chromium surface. Agitation may help.

Another method to remove surface chromium oxide from the metal is to reduce it to the metallic state by heat treatment, above 1050 ºC, with dry H2, which should be diluted with dry inert gas (≤ 5 % v/v H2) to obtain a safer gas mixture.