The 23-year-old, who spent two years at St. James' Park before being released in the summer, has now linked up with the Iron, penning a deal which will keep him at Glanford Park until the end of the season.
Former Barnet and Lewes wideman El-Mhanni joined the Magpies in the summer of 2016, and featured primarily for the club's under-23 side.
He made his first team debut for United in an FA Cup third round replay victory over Birmingham City in January 2017, before going on to feature in the fourth round defeat at Oxford United in what was his second and final senior outing for the Magpies.
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