If you mean the black hard anodizing on the upper and lower receivers, rail system handguards, etc, you shouldn't have any problems (unless your rifle has severe abrasions through this coating, and/or you expose it to (submerge in) salt water without rinsing)
The manganese phosphate (Parkerizing) found on the other parts is not as forgiving. Pay attention to areas where steel phosphate parts are in contact with aluminum anodized parts, especially in wear areas and those that trap water. Pins and springs on moving parts (around the extractor, and the charging handle latch, for example) might require more maintenance.
You might find yourself giving more than a routine cleaning, and I would use extra helpings of CLP in the above kinds of tight spots.
You might go ahead and get yourself a stainless barrel, and a hard-chromed bolt and carrier assembly. A condom over the muzzle might not be a bad idea, either.
Hope this helps...