Astaxanthin dipergunakan sebagai inhibitor organik karena dapat menurunkan laju korosi plat baja hitam dan ramah bagi lingkungan. Astaxanthin digunakan untuk memproteksi material plat baja hitam agar tidak terjadi korosi yang berlebihan. Laju korosi plat baja hitam dan efesiensi inhibitor didapatkan dari uji weight loss selama 30 hari perendaman dengan variasi konsentrasi inhibitor astaxanthin dari 0–200 ppm. Sedangkan mekanisme kerja inhibitor dianalisa melalui foto struktur makro dan pengujian FTIR. Didapatkan nilai rata-rata laju korosi terendah yaitu 0,06 mm/year dan efesiensi rata-rata tertinggi pada plat baja hitam yakni 55,31% dengan konsentrasi inhibitor 50 ppm. Inhibitor astaxanthin mampu teradsorpsi pada permukaan plat baja hitam dan juga menurunkan korosivitas air laut.

Astaxanthin is used as an organic inhibitor for its capability to reduce black steel plat’s corrosion rate and environmentally friendly property. Astaxanthin is used to protect black steel plate materialsfromexessive corrosion. Black steel plate’s corrosion rate and inhibitor’s efficiency ware obtained from 30-day weight loss test through immersion at varios concentrations of astaxanthinas inhibitor at 0-200 ppm. Meanwhile, the inhibitor’s actionmechanism was analized through macro-structure photos and FTIR test . its lowest averagecorrosion rate was 0,6 mm/year and its highest average efficiency was 55,58% for black steel plate with inhibitor at concentration of 50 ppm. The astaxanthin inhibitor adsorbed by the black steel plate’s surface alsoreduced the sea water’s corrosivity.