As part of a nationally-funded German research project, a new mounting procedure for maritime and offshore environments using adhesives has been developed and tested in laboratory and field applications.
Based on a benchmark study, suitable adhesive materials and surface preparation methods were evaluated. Furthermore, representative loading cases and environmental conditions were determined. Loading scenarios included tensile tests, shear tests, torsion tests, creepage, and fatigue tests. Specimens were tested under unaged conditions and aged conditions, whereby the aging procedures included temperature changes, humidity, and neutral salt spray tests. Six different metals/coating materials were tested as substrates for adhesive application. Metals included construction steel, stainless steel, and aluminum, whereas the coating materials covered epoxy, polyurethane, and polysiloxane.
The paper reports the details of testing and the results obtained for the different testing scenarios.
Welding for subsequent mounting of brackets onto fully coated surfaces (for example repair purposes, modification of equipment or subsequent fittings) raises a number of problems with respect to surface preparation, coating integrity, post-processing, heat transformation, esthetics, and health and safety. Two examples for subsequently welded holders onto coated surfaces along with the accompanying coating damages are provided in Fig. 1. An option for joining brackets is the use of mechanical fasteners. However, this solution often requires the drilling of pre-holes. This, in turn, leads to sealing problems, risk of corrosion and the reduction of the notch class.1
In order to reduce costs and working time and not compromise the existing corrosion protection system, a standardized procedure using high-performance adhesives has been developed. Brackets, and any attachments, are mounted directly to the topcoat without harming the coating or substrate. Part of the process is a non-destructive pre-evaluation test that verifies the required adhesion to the particular coating system.
Long-term stability of adhesives in an important aspect when investigating bondings. Of particular interest is the water/moisture absorption of polymer-based adhesives and the accompanying property modifications. This is one of the main reasons for the failure of adhesive bondings during their lifetime.2,3 In addition to water absorption, other factors, such as temperature levels, temperature fluctuations, high humidity, and salts, affect the long-term properties of adhesive bondings in marine environments.4
