Black bolts, also known as black oxide bolts, are often used in applications where corrosion resistance is desired. However, there are certain circumstances where they are not recommended:
When High Strength Is Required
- Black oxide coatings can reduce the tensile strength of the bolt.
- For applications requiring high strength, consider using plain steel bolts or bolts with other coatings like zinc plating or cadmium plating.
- Black bolts are generally not suitable for structural applications or applications where the bolt is subject to high stress.
When Chemical Resistance Is Needed
- Black oxide coatings offer limited chemical resistance.
- In environments with strong acids or bases, the coating can degrade, leading to corrosion.
- For applications requiring high chemical resistance, stainless steel bolts or bolts with specialized coatings are better choices.
When Electrical Conductivity Is Important
- Black oxide coatings are not electrically conductive.
- For applications where electrical conductivity is essential, plain steel bolts or bolts with conductive coatings should be used.
When Appearance Is Critical
- The black oxide coating can have a dull, matte finish.
- For applications where appearance is important, consider using stainless steel bolts or bolts with other finishes, like nickel plating or chrome plating.
When Lubrication Is Necessary
- Black oxide coatings can interfere with lubrication.
- For applications where lubrication is required, plain steel bolts or bolts with lubricated coatings are recommended.
In summary, black bolts are not recommended when high strength, chemical resistance, electrical conductivity, appearance, or lubrication are critical factors. For these applications, consider using alternative materials or coatings.
