Blackened screw refuses to deal with rust

Update:03 Apr 2020
Summary:

So, is this really the case? Whether the blackened scre […]

So, is this really the case? Whether the blackened screws are more prone to rust, this should be explained from the surface technology of the screws.
The process determines the prerequisite for poor blackening and anti-rust performance.
Secondly, the rust of small non-standard screw has a lot to do with the environment in which they are stored. The warehouse should avoid wet environments and the packaging must be sealed.
First of all, after producing blackened screws, one step in the process is to lubricate the screws. Some customers will request to wipe off the oil traces when purchasing, which precisely makes the precision small screws lose their protection, and it is easy to catch up with the humid environment such as rainy days during transportation and cause rust. But there are some ways to protect the blackened screws from rust.
A lot of procurement found that the blackened screws purchased were very easy to rust, and many companies have repeatedly received complaints accusing them of selling inferior products. Or, you can spray a layer of anti-rust oil when storing. It can be seen from the comparison of several commonly used surface treatments such as electrogalvanizing, cadmium electroplating, dacromet, etc. Although the cost of blackening is cheaper and beautiful, but its anti-rust performance is poor and it is easy to rust.
Blackening is a process of chemical surface treatment. The principle is to make an oxide film on the metal surface, so as to isolate the air and achieve the anti-rust effect.