Grade 8 vs. Stainless for corrosion

[flem0061]

Not really home or workshop but definitely project related...

I'm adhering 7 foot concrete curb stops to the bottom of a culvert with 14" SS 303 wedge anchor bolts. The bolts came with the nut and washer but no lock washer. I'd like to install them with a lock washer as I envision them being beaten with various objects flowing down the stream over the life of the installation. I can get Grade 8 lock washers with ease but stainless is not available locally in the quantity I need. Can anyone speak to the corrosion resistance of Grade 8 yellow zinc hardware? They will almost always be under water.
Thanks

 

[nat]

Stick with 300 series stainless fasteners. Even those will get some small corrosion. Mostly from free iron trapped on the surface. Passivation would help this, but really isn't necessary.