Ribbed flanged bolts are among the more expensive of the bolts range. One of their main purposes is to eliminate the human error factor – someone potentially forgetting to include the toothed washer into the assembly – by already building it into the bolt’s head. The ribbed bottom of the bolt’s head bites into the surface and that way secures additional clamp load.
There are, of course, downsides to that. First of all, such a bolt needs a flange of sufficient size to work. Over time, it will ease into the surface, loosing clamp load, while potentially damaging the flange surface. The gap between the threads of the nut and bolt will remain unaddressed throughout and be the main enabler for micromovements and vibrational loosening, as well as corrosion due to moisture that can easily get to the threads.
With a liquid threadlocker, such as one of the Loctite products, the gap which is the root cause of all the bolt failures, is effectively eliminated and sealed.