Get all the loose dirt, rust and grime off it, then take to the chromer. They'll strip and clean it the way they want for best end results. Better yet, call them and ask how they want it and when they want it.
sandblasting causes pits, and chrome does not fill pits, the real expense in chroming is the time it takes to smooth the metal before chroming, let the shop remove the chrome
Sandblast the back of bumpers and guards to remove loose rust and chrome. I usually do this and forgot one piece and it came back all crusty and ugly on the reverse side. If it starts to rust again or if the new chrome and copper plating did not get a good foundation, the rust will work around the edge.
Find a good chromer, take a look at his finished product if you can, ask him how he wants the parts, a lot of times blasting can add work or case odd effects in the metal, if you can not have a candid conversation with the guy, find one you can have one with. Send him a trial batch to see how he does.
The Chrome Shop in Menasha, WI. Steve Campbell / owner.
I have used his services for decades and not once have I been anything but super pleased. He delivers what he promises and when he promises. Quite an ethical craftsman for certain.
Advanced Plating in Nashville does great work. They were flooded and may still have a backlog of work. Worth the wait,I've never been disappointed with their quality.
Paul's Chrome plating in PA is very reliable and responsive to any of your concerns. They do excellent show chroming. The Finishing Touch in Illinois is also one of the best shops.
Pauls Chrome did a pair of trunk hinges for me and did NOT replace the hinge pin as promised. In fact he did not even remove the hinge pin and there is a shadow of no chrome where the hinges were closed when plated. I would not recommend him for any future jobs.
I would second Kube's recommendation of the Chrome shop in Menasha Wisconsin. They do beautiful work. I have been taking my stuff there for over 20 years. Dave/Green Bay