Chassis prep.

[boygenius]

I have a question. I have stripped my chassis and sand blasted it to bare metal in order to apply POR-15. After degreasing the chassis I applied the metal etching spray. The entire chassis is the same dull gray color except for the drivers side floor pan which still looks like sand blasted steel.. I replaced the floor pans about two years ago and the car has been sitting ever since. Both the floor pans came from the same shop. Is there a coating on one of them. Could they be differant metals if they came from two different batches of floor pans. What should I do.