Bolt of surface treatment is probably black dyed, that is it seems that it only black dyed in SCM material fabric.
If to consider the rust prevention Uniqlo and chromate, there are other surface treatment.
But wherever he is Masu rust.
I think that the surface-treated bolt suitable for the intended use is good.
Also screwed in the other person is like that not screwed to the base of the head of the cap bolt, but is impossible.
Or cap bolt dedicated lock washer in combination with washer, combination of the tapered washer is usually none.
Right people specific place, you should see better how to use even that was quite to recommend because there is a kind of increase the knowledge obtained to buy because it is surprisingly inexpensive, so we have been sold the "List of the screw" is itself to potential up.
It is difficult when the bolt relationship goes packed.
Material and hardness, etc. (yes, the surface treatment is) well to examine it is recommended that you choice.
We hope you are able to for your reference.
1 month black oxide film rather not matter or something does not have Toka with was rusty at 2 degrees of rain. I think that falsehood's not impossible on the experience up to now! ... I can not trust be're using really SCM material and it is this quality