<p>The pipeline is a primary source of hydrocarbon transportation in the offshore oil and gas industry; however, corrosion-induced metal loss from pipes due to the hostile marine environment poses risks not only to the pipeline's mechanical properties, but also potentially leading to marine ecotoxicity. Therefore, this work aims to study the effect of seawater environmental parameters, such as temperature and salinity, on the external metal loss, microhardness, and marine ecotoxicity of offshore pipes samples. The immersion test was conducted for the period of 28&#xa0;days, replicating various artificial environments with different temperature and salinity values. For the microhardness study, the Vickers microhardness tester was used. Additionally, the life cycle assessment methodology was applied to study the effect of metal loss from pipes on marine ecotoxicity. The results showed that corrosion-induced metal loss in seawater affects mechanical properties and has a significant impact on marine ecosystems. As the salinity rises from 33.18 to 61.10 ppt, there is a 30% drop in metal loss, a 3.6% drop in microhardness, and a possible drop in marine ecotoxicity from 2.16 × 10^–1 (1,4 DB EQ/FOOT) to 1.5 × 10^–1&#xa0;KG (1,4 DB EQ/FOOT). Additionally, we observed that a small 10&#xa0;°C reduction in solution temperature led to a 76.13% decrease in metal loss, a 9% improvement in microhardness, and a notable decrease in marine ecotoxicity from 4.1316 × 10^–1&#xa0;KG (1,4 DB EQ/FOOT) to 2.1616 × 10^–1&#xa0;KG (1,4 DB EQ/FOOT). Furthermore, this study employed response surface modelling (RSM) to find out the best seawater parameters at which offshore pipe has maximum performance, and the lowest marine ecotoxicity. The desirability factor was 0.963. Experimental validation demonstrated approximately 2.63% error for metal loss, 0.48% error for microhardness, and 2.66% error for marine ecotoxicity. The findings of this study can be used for offshore project planning around Peninsular Malaysia.</p>