Many systems can be converted and used for different applications not initially planned. This is the case for production wells, sometimes converted into water injection wells and for which the production tubing material selection is clearly not adapted for prolonged contact with natural seawater. Oxygen removal treatment must be applied but precise control is not obvious and excursions above zero or close-to-zero oxygen can occur. The production tubing material S13%Cr are known to be sensitive to dissolved oxygen excursions in seawater, but data from the literature cannot precisely help in defining the allowed limits of use. Exploring the possibility to convert a production well into a treated seawater injection well then requires a careful assessment of the corrosion resistance limits of the involved alloys. A series of corrosion tests in treated seawater were designed to assess the limits of use of fast connector made of alloy UNS S41427. The corrosion tests were performed both at laboratory scale and on full-scale fast connectors in a treated seawater flow loops simulating service conditions. For all the performed tests, maintaining the dissolved oxygen content (DOC) at 15 ppb and below never led to localized corrosion and has been considered as a safe condition in terms of corrosion risk for alloy S41427 at ambient temperature. It was found that prolonged dissolved oxygen content (DOC) above 30±10 ppb may lead to initial crevice corrosion after only 4 h of exposure. Globally, a very good correlation between the laboratory and the full-scale test results was found. The critical crevice potential for alloy S41427 was significantly affected by the cleaning process of the tested coupons, while the stop of the corrosion was always measured for potentials reached at DOC < 10 ppb. The proposed methodology, involving both laboratory and full-scale tests, allowed to precisely quantify the limits of use of UNS S41427 in treated injection well. It could be used for any other material and applications to help at designing adapted and reliable engineering diagrams for material selections. .