Surface Conditions of Adherend

The effecting of intimate contact of the surface of the adherend to be bonded and the adhesive depends on two major factors  

Even polished, lapped, metal surfaces have irregularities of about 10 m and such pits can trap air. If no air is trapped in the pits of the metal then one can see that the surface wetting and adhesive coverage would be complete. Any entrapment of air will lead to incomplete adhesive/metal coverage and much will depend upon the contact angle of the adhesive and capillary attraction. The critical angle for perfect contact between adhesive and substrate approaches zero. 

The viscosity of the adhesive is obviously a significant factor in the correct application of the correct and complete contact layer on the adherend. A number of adhesive factors will need to be addressed  

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Monitor surface condition of adherend in critical areas Monitor application of adhesive in critical areas Monitor adhesive curing regimes... 

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