Coulomb's law has of the gravitational of form. Experimentally established the existence of gravitational-electromagnetic resonance, see, eg,:
https://hal.archives-ouvertes.fr/hal-01329094v1
https://hal.archives-ouvertes.fr/hal-01232287v1
https://hal.archives-ouvertes.fr/hal-01326265v1
Therefore, the electromagnetic interaction is a special case of gravitational interaction.