The PAO/MgO nanofluids-based dielectric fluid DF(MgO-20) has significantly increased corrosion resistance as a coating. Electrochemical studies show that the DF(MgO-20) coating has protection efficiency of up to 99% for steel, copper, and aluminum. This coating is capable of providing corrosion protection for steel samples for up to 120 h in salt spray tests, and printed circuit boards (PCBs) for more than 20 days in salt spray tests in accordance with the ASTM B117 standard. The DF(MgO-20) coating fully meets the moisture resistance and fungal resistance standards required by the MIL-1-46058 C standard. The coating also demonstrates water displacement, meeting the requirements of the MIL-PRF-81309G standard. The DF(MgO-20) coating is able to protect electronic equipment working in underwater environment for up to 20 days. The aforementioned outstanding protection properties are achieved thanks to the nanofluid effect of the DF(MgO-20) dielectric fluid with the presence of MgO nano-additives that increase its overflow ability. The coating penetrates deeply and adheres tightly to the metal substrates, helping to separate them from moisturizing agents and corrosive agents. The research results aim to apply this coating to protect electronic equipment working in the tropical marine climate of Vietnam.