The sour corrosion product (i.e. iron sulphide) exhibits different morphologies under different operating conditions and possess different crystal structures and oxidation states. Developing a model to understand the growth mechanism of different forms of the sour corrosion product is essential in predicting corrosion rates and mitigating scale formation in sour environment. This paper presents a new approach wherein the nano-crystalline iron sulphide (mackinawite) scale formation is modeled by the nucleation and growth of the scale crystals. Ignoring any solid state reactions that could form iron sulphide in undersaturated solutions the supersaturation level quantified the extent of nucleation followed by diffusion controlled crystal growth. The scale morphology in terms of the volumetric porosity and their influence on the predicted sour corrosion rates were studied under stagnant conditions.Key words: sour corrosion predictive modeling iron sulphide nucleation growth porosity morphology