Sagebrush posted:

Just for future reference, you want zinc plated bolts for your bike. Not stainless, not galvanized, not black oxide. Bright zinc plated.

Black oxide is a temporary coating that really only prevents corrosion while the bolts are sitting in a bin at the store. Those bolts will all rust within a year or so of being exposed to the weather.

Stainless is only necessary in situations like marine environments where you have to deal with heavy chemical corrosion, or where you expect the part to be pounded on and damaged and a zinc plating would eventually flake off. Stainless steel is not as strong as the plain steel underneath the plated bolt. It's fine for non-structural parts, as people have mentioned, but not to replace things where the bolt snapping would be immediately dangerous.

(There are different grades of stainless fasteners with different strengths, of course, but the bag of stainless bolts on eBay is not going to be the strong stuff).

Galvanized bolts are dipped in molten zinc and have very high corrosion resistance, but the heavy zinc coating means they only work with galvanized fasteners. You can't (properly) put a galvanized bolt into a tapped hole in your engine case.

Zinc plated bolts are electroplated, leaving a thin but strong protective layer that doesn't change the thread geometry to any significant degree. They can be made with the strongest steel and can replace the original fasteners one to one. They are also usually a little cheaper than stainless. Best choice all around.

Note that some of the weird backwards countries call all zinc coated bolts "galvanized" and you might have to figure out whether they are talking about the hot dip process or the electrical process. Plated bolts are bright and shiny and smooth, while galvanized ones are gray and have a mottled pattern and are kind of rough. Fortunately in America we have two different terms so we don't have to deal with that crap.