Significant issues arise when the chloride ions are on higher side in concrete mixture. These chloride ions break down the submissive layer due to their electrochemical nature. This protects the reinforcing bars without varying the pH. Hydrochloric acid is produced, which is a chemical process when these chloride ions come in contact with steel and the surrounding passive materials. This acid corrodes the steel reinforcement, leading to concrete cracking, spalling, and eventual failure. Therefore, chloride-induced corrosion is a major issue affecting the durability of reinforced concrete (RC) structures. This study investigates the ingress of chloride ions in copper slag concrete. Corrosion tests were conducted using thermo-mechanical treatment (TMT) steel. A study on the Rapid Chloride Ion Penetration Test, conducted according to ASTM C1202, found that the values for all grades of concrete, both with and without incorporated copper slag, fell into the “very low” category. An important observation was that the addition of slag significantly reduces the pores in the concrete, making it impermeable.