Corrosion Behavior Of Sn-0.7Cu Under Different Artificial Sweat Conditions

Solder materials play an important role in the electronics industry,especially in complex circuits and mechanical connections.Tin alloys are used to connect various surfaces and interfaces,which can easily lead to the failure of electronic devices due to corrosion.In daily life,electronic devices used for a long time are inevitably affected by human sweat.With the functionalization and integration of wearable devices,circuit connections are highly likely to be corroded by human sweat,so the reliability of wearable devices faces challenges.Therefore,it is of great theoretical value and practical need to study the corrosion behavior of tin alloy in human sweat.In our work,experimental planning was carried out based on the practical application background of earphones,and the corrosion behavior of conventional welding material tin alloy(Sn-0.7Cu)in artificial sweat was studied.Considering the application of earphones in closed ear canals,the experimental conditions were set in combination with the temperature,p H value and other physical and chemical properties of sweat produced by human body under different activity states such as sitting and running,as well as the change of ambient temperature.The effects of different p H values and applied potentials on the corrosion behavior of Sn-0.7Cu in artificial sweat were tested by three-electrode electrolytic cell device and by Gamry electrochemical workstation in a 20 ℃ constant temperature solution environment constructed by water bath.The surface morphology and chemical composition of the corrosion products were analyzed by three-dimensional laser confocal microscope,scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The results showed that stable passivation zone existed in the potentiodynamic polarization curves in artificial sweat at three p H values,that is,passivation film can be formed on the surface of Sn-0.7Cu during potentiodynamic polarization.At the same applied potential,the corrosion resistance of the Sn-0.7Cu passivation film increased with the increase of p H value of artificial sweat.In artificial sweat at the same p H value,the corrosion resistance of Sn-0.7Cu passivation film increased with the increase of applied potential.On the basis of the design idea of normal temperature environment,acid and alkaline artificial sweat were selected for experiment.According to the different body temperature of human body in different activity states,combined with the influence of environmental temperature,the experimental temperature is designed as 20 ℃,30 ℃ and 40 ℃,and three constant temperature experimental environments are constructed through water bath.Gamry electrochemical workstation was used to test the effect of different temperature conditions and different applied potentials on the corrosion behavior of Sn-0.7Cu in acid and alkaline artificial sweat.The surface morphology and chemical composition of the corrosion products were analyzed by three-dimensional laser confocal microscope,scanning electron microscope and energy dispersive spectrometer.The results showed that there were stable passivation zones in the electrokinetic polarization curves of both acidic and alkaline artificial sweat under the three temperature conditions,that is,Sn-0.7Cu could form passivation film structure in the potentiodynamic polarization process.When the temperature is 30 ℃,the passivation film generated in acid and alkaline sweat has the best corrosion resistance.The corrosion resistance of Sn-0.7Cu passivation film formed in alkaline artificial sweat was better than that formed in acidic artificial sweat at the same temperature and the same applied potential.In artificial sweat at the same temperature and p H value,the corrosion resistance of Sn-0.7Cu passivation film increases with the increase of applied potential.As the smart electronic wearable devices such as earphones are actually in the atmospheric environment,the relative humidity of the environment and the standing time are taken as parameters to conduct the standing experiment on Sn-0.7Cu with acid and alkaline artificial sweat.The surface morphology of corrosion products was analyzed by scanning electron microscope,and the corrosion rate was analyzed by weight loss method.The effects of environmental relative humidity and standing time on the corrosion behavior of Sn-0.7Cu in acid and alkaline artificial sweat were investigated.The results showed that when the acid and alkaline artificial sweat crystals are uniformly covered on Sn-0.7Cu under different humidity conditions,artificial sweat thin film environment occurred on the alloy surface and initiated corrosion,and the corrosion rate increases with the increase of environmental relative humidity.In both acidic and alkaline artificial sweat coating,Sn-0.7Cu corrosion occurred in the natural environment without wind,and the corrosion degree increased with the increase of the coating time.After the first cycle,the corrosion degree of Sn-0.7Cu in acidic artificial sweat was significantly stronger than that in alkaline artificial sweat.