Climatization, adherend

For the sake of completeness, climatization deserves attention within the context of the surface post-treatment. With fluctuation of temperature and humidity, water condensation on the adherends is possibly limiting the adhesive properties. 

The amount of data available in the literature involving long exposure times in hot humidity of metal adherends other than aluminum is also quite limited. Brockmann ) has compared the rate of degradation on steel joints exposed to 95% RH conditions for four months to the same time exposure in 40°C water or the natural climate of North Germany. The environments were decreasing in severity on the joints in the order 40°C >95% RH > the natural atmosphere. Exposure of titanium joints to 95-100% RH was used by Mahoon(i36) to discriminate the relative durability imparted by varying surface pretreatments. 

When exposed to weather, structural adhesives rapidly lose strength during the first six months to one year. After two to three years, the rate of decline usually levels off, depending on the climate zone, adherend, adhesive, and stress level. Figure 7.37 shows the weathering characteristics of unstressed epoxy adhesives to the Richmond, VA, climate. 

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