Definition of Black Oxide Coating
Black oxide coating is a conversion coating applied to steel fasteners, including screws and bolts. You use it to add a thin, black finish that offers mild corrosion resistance and reduces light reflection. The process involves immersing cleaned parts in a hot alkaline solution that converts the surface into magnetite (Fe₃O₄). Black oxide does not add significant thickness, so you keep original dimensions and thread fits.
You often choose it when you need a uniform look, slight wear resistance, and better oil adhesion. Engineers and buyers in fasteners prefer it for parts in controlled or indoor environments where heavy corrosion protection is not required.
Why It Matters for screws and fasteners
Black oxide coating helps you avoid misfits. It does not change thread tolerances. You keep design precision while adding a uniform finish. If you need a consistent appearance across batches, this coating fits.
You gain mild corrosion resistance when you pair black oxide with oil or wax after treatment. You lower risk of surface rust in indoor or low-humidity settings. This coating also reduces light glare on assemblies.
You save cost when you do not need heavy plating. You streamline processes because the coating bath uses common chemicals and short cycle times.
FAQ
What is black oxide coating and how does it work?
Black oxide coating converts the steel surface into magnetite via a hot alkaline solution. This thin layer bonds tightly without changing dimensions. You see a black finish that holds oil and offers mild rust protection in controlled settings.
Can I use black oxide coating on screws exposed outdoors?
Black oxide alone provides only light corrosion protection. If you expose parts outdoors, add oil or wax after coating and consider additional sealing. For harsh environments, you may select more robust coatings such as zinc plating or powder coating.
Does black oxide affect screw dimensions or thread fit?
No. Black oxide adds only a few microns and does not alter overall dimensions. You keep thread tolerances unchanged. This makes it a good choice when precise fits matter and you need a consistent dark finish.
