Purpose – The purpose of this paper was to use the barnacle Amphibalanus amphitrite reared in the laboratory to investigate the effects of juveniles on corrosion behaviour of three stainless steels (SS): UNS S31600, N08904 and UNS S32760. Design/methodology/approach – Barnacle larvae were maintained in a laboratory until they reached the cypris larval stage. A total of 100 cyprids were added to four individual containers; each SS coupon (70 × 50 × 2 mm3) was immersed into the containers. After the cyprids attached to the coupons, juveniles were reared for 21 days with the microalgae Skeletonema costatum (Greville) Cleve. Values of open circuit potential (OCP), breakdown potential (Eb) and polarisation resistance (Rp) were evaluated, along with surface examinations. Findings – OCP differences between barnacles and control coupons were not apparent. However, the lowest values of Eb and Rp were observed in the presence of juvenile barnacles, demonstrating the SS corrosion caused by these organisms. Crevice corrosion around the base of the barnacles was detected during visual inspections, despite the small size of the barnacles and the short duration of the experiments. Originality/value – The A. amphitrite assays were useful as a tool for testing corrosion behaviour of the SS under laboratory conditions. This was the first study to test the use of this common protocol in anti-fouling research as a method to study marine biocorrosion.