Removing stains
 

Hi,
I'm just about to finish my first deck. It's pretty nice cedar deck with a pergola on the corner.
Unfortunately not long ago, I had to cut off a couple of lag bolts and the iron dust spread all over my decking. With the help of a light rain over the night my decking is deep stained all over. I to clean it with soap and warm water, I tried with powder detergent someone suggested, I tried power washer, I tried a small area with baking soda which make it worst and finally I started to sand it.
It was a pain , it took two hours to remove the stains from two square yards and I stopped.
My deck is pretty large and with my small machine will take a week to finish it.
Is somebody there who encountered the same problem ?
Is there on the market some stripper or anything can remove those stains ?
Any ideas would be highly appreciated.
Thanks,