Gas-Tight Joint
A gas-tight joint is the connection formed when the metal surfaces in a correctly made crimp are pressed together so hard that no air can get between them. Because oxygen cannot reach the contact area, oxidation cannot start and the contact resistance stays stable for years.
A copper surface is covered by a thin oxide layer within seconds in open air, and that layer is an insulator. The pressure applied during crimping does two things at once: it breaks the existing oxide film and presses the clean metal underneath so close to the neighbouring surface that no gap remains to hold oxygen.
- Why a loose connection degrades: micro gaps remain between surfaces that have not been pressed hard enough, oxide grows, resistance rises, heating starts and the heating accelerates the loosening.
- Why measurement misleads: a freshly oxidised connection can look good on a low-current ohmmeter; it collapses under real load.
- How to verify: measure the voltage drop between the two ends of the connection under load.
The same principle applies to lugs, ferrules and connector pins. On vehicle and work machine installations operating in damp or salty environments, additionally closing off the connection area with adhesive-lined sleeving or a suitable protective compound supports the protection the crimp provides.
The context in which this term is used: Installation, redundancy and field continuity