Internal Hex Thread Male Plug

When choosing the surface treatment for the Internal Hex Thread Male Plug, the main factors to consider are the usage environment, strength requirements, assembly convenience, and cost budget.

（1）Environmental corrosiveness

Galvanization typically lasts for 72 to 100 hours in salt spray tests; zinc-nickel alloy can last up to 720 hours; and Dacromet can last 1000 to 2000 hours. The more severe the environment, the higher the corrosion resistance grade should be selected.

（2）Strength grade

If the strength of carbon steel or alloy steel Internal Hex Thread Male Plug is ≥ 10.9 grade, ordinary galvanization cannot be chosen.

Strength grade Available surface treatments

≤ 8.8 Regular galvanizing, blackening, phosphating, nickel plating are all available

≥ 10.9 Blackening, phosphating, Dacromet coating, zinc-nickel alloy (without hydrogen embrittlement process), hot-dip zinc coating

（3）Risk of thread engagement

If the Internal Hex Thread Male Plug and the interface material are prone to develop thread galling, it is recommended to use phosphating or nickel/chromium plating to improve lubrication.

（4）Cost budget

From low to high, they are: blackening treatment, ordinary galvanization; Nickel plating, phosphating; Dacromet, zinc-nickel alloy, hot-dip zinc

The stainless steel material itself does not require surface treatment, but its cost is much higher than that of carbon steel with coating.

Frequently Asked Questions

（1）Does the surface treatment affect the thread fit or sealing performance of the Internal Hex Thread Male Plug?

There will be a slight impact. Coatings such as galvanization and Dacromet will increase the thickness of the threads. Therefore, we will control the coating thickness within 5 to 15 micrometers to ensure that it does not affect the fit.

（2）Can you provide a black finish that is also corrosion resistant?

Yes. The appearance of Black Oxide is black, but its rust prevention ability is relatively poor and it requires oil coating. It is recommended to use Black Dacromet or Black Zinc, which not only have a black appearance but also have much better rust prevention performance than the black finish.

（3）Which finish is best for applications where the plug will be frequently removed and reinstalled?

Recommend Phosphating or Nickel Plating. These two surface treatments are relatively smooth and do not cause thread galling during assembly and disassembly.