RETRACTED: Pre-threaded hole friction stir spot welding of AA2219/PP-C30S sheets

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Authorship irregularities were discovered for this paper. Changing authors after submission without permission from the editor is against the journal policy as it is stated in the Guide for Authors. During revision, two authors were added and one author was removed. The author responded to requests for clarification on these points, but those explanations did not satisfactorily address the concerns. As such the Editor-in-Chief has decided to retract the article. The scientific community takes a very strong view on this matter and apologies are offered to readers.