ESD protection for 3.3v sram chips

I'm having a problem with our 3.3v sram chips getting corrupted on power up. The control panel they are mounted on is a 12vdc unit that draws up to .6 amp of power. The 12vdc is regulated down to 5v, then down to 3.3v. These control panels fit into a rack where the back plane supplies power to up to 6 controllers. I don;t have a problem when there is only 1 controller in the rack, but if I get up to 5 controllers, the back plane could have 4-5 amps of 12v power running through it. Now when I power up the controller the ram chips get corrupted. What do you have to better protect the low voltage circuit. Possible solution could be on the 12v side or 3.3v side.