The paper investigates the effect of silver coating on the corrosion behaviour of magnesium alloy NZ30K alloyed with 0.09 wt.% Ag in Ringer–Locke solution. Samples of the alloy under study are plated with a silver layer of 200–300 nm and 500 nm thickness using the DC-magnetron sputtering system equipped with a circular silver source and target (of 50 mm in diameter) in a gas discharge. An unbalanced magnetron in a 600 mA DC mode at a voltage of 400 V is used. The silver coating at a constant magnetron power of 240 W and a bias voltage of 100 V is applied. The deposition time of a silver layer of 200–300 nm is of 5 minutes, and for 500 nm, is of 15 minutes. As found, the steady-state value of the corrosion potential $E_{cor}$ for the samples of the studied alloy clad with a silver layer of 200–300 nm is formed during 2060 s from -1.418 up to -1.4449 V, and with 500 nm layer, during 1880 s from -1.433 up to -1.465 V. As recorded, the steady-state value of $E_{cor}$ for both samples is established in two stages. As found, the rate of shifting of the potential $E_{cor}$ for the studied samples in the negative direction at the first stage is of 0.062 and 0.034 mV/sec, respectively. As shown, the rate of shifting of $E_{cor}$ in the negative direction for the sample with a coating thickness of 200–300 nm at this stage is by 1.82 times higher than for the sample with a coating thickness of 500 nm. This is due to a larger number of linear and point defects over the coating with a thickness of 200–300 nm than with 500 nm and more intense contact corrosion. During the transition from the first stage to the second one of the formation of the stationary value of the potential $E_{cor}$, its abrupt fluctuation of up to 5 mV is observed that is associated with the delamination of the coating from the alloy in the vicinity of corrosion pits on the surface of the samples due to the contact and crevice corrosions and the mechanical effect of hydrogen bubbles released at the cathodic areas (of silver coating). As shown, the steady-state value of the potential $E_{cor}$ for the samples of the alloy under study with a coating thickness of 200–300 nm and 500 nm is more positive by 9 and 7%, respectively, than that of the sample of the same alloy without a silver layer. This proves that, by applying silver coatings with different thicknesses, it is possible to control the rate of corrosion dissolution of NZ30K alloy with Ag (0.09 wt.%) in Ringer–Locke solution, and this approach can be used for the fabrication of biodegradable implants for the treatment of broken human bones.