The black stuff mechanics use to grease bolts is called graphite. It’s a lubricant that helps to prevent rust and corrosion on metal surfaces.
Other related questions:
Q: What grease is used for bolts?
A: There are many types of grease that can be used for bolts, depending on the application. For example, lithium grease is often used on door hinges, while greases specifically designed for use on high-temperature applications or in wet environments may be used on other types of bolts.
Q: Should you put grease on bolts?
A: Grease can help to protect bolts from corrosion and make them easier to remove, but it is not always necessary.
Q: How do you blacken bolt heads?
A: There are a few ways to blacken bolt heads, but the most common method is to use a black oxide kit. This kit will usually come with a black oxide solution and a blackening agent.
Q: What do you put on bolts so they don’t rust?
A: There are a few things you can do to prevent rust on bolts. You can apply a rust-resistant coating, such as paint, oil, or wax. You can also store the bolts in a dry, airtight container.