This report is produces in cooperation with Terma Aero structures. The purpose is determining the reason why there are areas with out adherence in Terma’s production of winglets for golf steam business jets. The focus of this report will be on the three components (epoxy resin, primer and aluminium plates), and the three production steps: retention time in the cleaning process of aluminium, time between cleaning and application of the primer as well as the influence of the humidity in the room, where the primer is added The analysis of the three components was done by Atomic Force Microscopy and Infrared Spectrometry. The result of the analysis could not determine anomaly in the componets that could explain the adhesive problem. To determine any interactions between the three factors, where there made two statistic experiment plans with full factor experiment The experiment did not determine any correlation between the three factors and the adherence problem. The result did however determine a correlation between the peel strength and the humidity, higher humidity did result in higher peel strength.