The surface potential decay time is related to the number of collisions neutral gas particles with the polymer surface per unit area per time. [Display omitted] • We measured surface potential of an insulating sample using Kelvin probe system to investigate the neutral gas effect on charge compensation. • Gas cluster ion beam was used to accumulate charges and to minimize damage to the sample surface. • Neutral gas effect on surface charge of insulating sample depends on the type of injection gas. • Surface potential curves were fitted by exponential decay function to obtain decay time. Surface charging of an insulating sample has been a significant issue in surface analysis. In time-of-flight secondary ion mass spectrometry, the charge also accumulates on the surface of an insulating sample by the primary ion beam, such as an argon gas cluster ion beam. Such charging can lead to not only degraded mass resolution but also low image resolution, and thus it is necessary to compensate for surface charging of insulating sample. Therefore, several efficient methods have been proposed for charge compensation, such as using a low-energy electron flood gun, applying a bias voltage to the sample stage, and using a gas flooding system. Here, we measured the surface potential of a polymer film to investigate the gas effect on the charge compensation using a Kelvin probe. During the measurements, the chamber pressure was gradually increased by injecting gases, such as He, Ne, Ar, N 2 , and O 2. We found that the injection gas may reduce the surface charging of the sample, depending on the type of gas. [ABSTRACT FROM AUTHOR]