Na armiranobetonskim konstrukcijama izloženim agresivnom okolišu često nastaju oštećenja uslijed korozije armature izazvane kloridnim ionima. Oštećenja nastaju u obliku pukotina i odlamanja zaštitnog sloja betona uslijed bubrenja produkata korozije, što nepovoljno utječe na nosivost i trajnost konstrukcije. Povrh toga, površina poprečnog presjeka armature smanjuje se istovremeno s procesom degradacije betona. No, oštećenja se javljaju neposredno nakon depasivacije čelika uslijed kritične koncentracije kloridnih iona u blizini armature. Vrijeme koje je potrebno da kritična koncentracija kloridnih iona prodre do armature naziva se faza inicijacije, a osnovni cilj ovog rada je procjena njezinog trajanja. Trajanje faze inicijacije moguće je predvidjeti ukoliko se u obzir uzmu transportni procesi koji se odvijaju kroz zaštitni sloj betona. Najvažniji fizikalni procesi vezani uz fazu inicijacije su transport kapilarne vode, kloridnih iona te topline. Stoga je u okviru ovog rada razvijen 2D numerički model pomoću metode konačnih razlika, koji simulira navedene transportne procese. Primjena modela pokazana je na numeričkom primjeru u kojem je kvadratni poprečni presjek armiranobetonskog stupa izložen agresivnim morskim uvjetima. Proračun je proveden kako bi se istražio utjecaj širine pukotina na trajanje faze inicijacije. Numerički rezultati pokazuju da raspucalost zaštitnog sloja betona značajno smanjuje trajanje faze inicijacije, a samim time i uporabni vijek konstrukcija. Reinforced concrete structures exposed to aggressive environmental conditions often exhibit damage caused by chloride-induced corrosion of reinforcement. The damage occurs in the form of cracking and spalling of the concrete cover due to the expansion of corrosion products, which adversely affects the bearing capacity and durability of structures. Moreover, the cross-sectional area of reinforcement decreases simultaneously with concrete deterioration. However, the damage occurs shortly after steel depassivation caused by critical chloride concentration in the vicinity of the reinforcement. The time necessary for critical chloride concentration to reach the reinforcement is called initiation phase and the main objective of this paper is to estimate its duration. The duration of the initiation phase is possible to predict if transport processes, which take place through the concrete cover, are accounted for. The most important physical processes related to steel depassivation are the transport of capillary water, chloride and heat. Therefore, the development of a 2D is presented in this paper. The model is based on the finite difference method and simulates aforementioned transport processes. The application of the model is shown on a numerical example in which a square cross-section of a reinforced concrete column is exposed to aggressive maritime conditions. The analysis is carried out to investigate the influence of crack width in concrete cover on the duration of the initiation phase. The numerical results show that the cracking of concrete cover significantly reduces the duration of the initiation phase, and, consequently, the service life of structures.