In the interest of preventing future corrosion consider also replacing the o-ring on the socket where it enters the housing.

On this car the o-rings were likely original and were fitting very loosely. They were likely allowing moisture to enter the housing.

Find a suitable replacement in your o-ring kit or at the local hardware store.

Coat the o-ring with a light coating of silicone grease to ease re-installation as the new o-ring may be a very snug fit. Also, the grease will help improve the seal and preserve the o-ring over time.