Corrosion of reinforced concrete structures is caused by many factors, such as carbon dioxide, chloride, and moisture. These factors cause the steel reinforcement in concrete to corrode, shortening the life of the structure. Therefore, the method to prevent deterioration and reduce structural severity needs to be studied. In this study, the objective was to compare the corrosion rates measured by LPR with the actual corrosion by visual inspection of chloride-exposed reinforcing steel. Reinforcing bars were embedded in concrete using Portland composite cement (PCC) with water/binder ratios of 0.4 and 0.6, fly ash was used to replace cement at 0% and 30% by weight of binder. Sodium chloride was added to the concrete using ratios of 0%, 0.75% and 1.5% (Cl−) by weight of the binder. The tests consisted of moisture content, a four-point Wenner probe, linear polarization resistance (LPR). Concrete with a water-to-binder ratio of 0.6 showed lower electrical resistivity and higher corrosion rates than these of water-to-binder ratio of 0.4. Using fly ash increased electrical resistivity and reduced corrosion. Higher chloride levels increased electrical resistivity in PCC and FA concrete but decreased in OPC concrete. Higher chloride content also increased corrosion rates. PCC concrete showed higher electrical resistivity and lower corrosion rates than OPC. When comparing the two methods, it was found that samples without chloride showed high corrosion rates, while the chloride level results showed no rust. The Potentiodynamic Polarization Resistance (PPR) test method must also be utilized to calculate the Stern-Geary constant (B) and calculate the corrosion rate for better results.