In this study, a penetrating silane sealer with different coverage rate was applied to concrete with w/c ratios of 0.35, 0.45, and 0.55. The rapid chloride penetration test (RCPT) that under an applied voltage to accelerate chloride ion migration into concrete was performed to assess the resistance provided by surface treatments (penetrating silane sealer) to chloride migration into concrete. The resistance to chloride penetration in treated concrete is controlled by both the substrate and the coverage rate of dosage. The charge passed obtained from RCPT and the total chloride penetrated into concrete from the chloride profiles were calculated and compared. The results show a linear correction between the charge passed and total chloride in concrete. The procedure of determining the resistance to chloride for surface-treated substrate concrete by measuring the charge passed is valid. (C) 2004 Elsevier B.V. All rights reserved.