Well, I'm going to buck the trend on the use of ACF50, or at least, to qualify it.
Anyone thinking plastering it on your bike will protect it sufficiently may be in for a disappointment. I ride year round and none of my bikes have escaped degredation in winter as salter roads play havoc with any exposed metalwork, and particularly with engine casings where modern water based paints might be used. Yes, it will work for a short while, but unless you're prepared to wash your bike off at the end of the day, inspect and reapply as necessary, it won't protect as well as other products, at least not in the parts exposed to gravel, mud and other debris sprayed up by the wheels onto those areas prone to damage through pin holing of paintwork etc.
I still use ACF50 and liberally coat all exposed fastenings and metal parts as well as engine casings, electrical wioring connections andareas not exposed to damage from road debris. However, by far the better winter protection is given by the liberal application of Lanoguard or XCP rust blocker. Both dry to form a thicker skin than ACF so offer better impact protection against paint damage. Both last longer between reapplications (typically I only need to apply Lanoguard twice over the winter months and when I used XCP, I found with regular bike use, I used to have to re-apply sparingly every 8 weeks or so).
As my bike's sump area and underside of main engine casings are already exhibiting paint bubbling, as are the areas surrounding the header pipe fixing to the cylinder heads, I will be far more liberal in the Lanoguard application and repeat applications regularly there until a good thick coating has built up. Later next year I aim to remove the flaking paint, kill the corrosion and use simple good old Hammerite on the underside which gives far better protection than the useless paint finished bike manufacturers are forced into using these days, but still will use Lanoguard in winter.
Main thing is if you ride salted roads and fail to wash your bike off every single ride, you will inevitably end up with some corrosion. I've ridden year round for over 35 years and in all that time haven't found a single wonder product that guarantees immunity to corrosion unless these steps are followed.
