In order to study the influence of high humidity

sustained rain

and fog on hydrophobicity of composite insulators’ surfaces

we conducted experiments with new composite insulators soaked in solutions of different p H to simulate the target conditions

and analyzed the samples using the leakage current method and the Fourier transform infrared spectroscopy. It is found that

for the samples in continuous immersion

both RMS leakage current and tanδ on their surfaces increase with the immersion duration

while the immersion in alkaline solution more remarkably results in RMS leakage current and tanδ than that in acid（H2SO4） solution and neutral solutions（deionized water and Na Cl solution）. The map of infrared spectrum shows that

for the silicone rubber immersed in alkaline solution

the main peak area and the maximum peak of both the silicone main chain and the main and the main hydrophobic groups are larger than those in the other tested solutions peak. Thus

alkaline solution can break the bonds of the main hydrophobic groups in silicone rubber more easily

i.e. alkaline solution can easily remove the surface hydrophobicity of insulator

which is barely affected by deionized water and neutral Na Cl solution.