Page 65 - Handbook of Adhesion Promoters

58 Substrates - Surface Condition and Treat-

Figure 4.5. Schematic illustration of the surface changes after various cleaning processes; (a) as received sample,
(b) after alkaline etching and (c) after alkaline etching followed by acid cleaning. [Adapted, by permission, from
Gohru, SS; Attar, MM; Ramezanzadeh, B, Prog. Org. Coat., 87, 52-60, 2015.]

• if adherent is subject to any action which does not seem to change its chemistry
(for example, abrasion, cleaning, etc.), it should always be considered that physi-
cochemical properties of surface have been modified and the surface after such
modification may behave differently
• surface aging (exposure to oxygen or environmental stressors) usually produces
completely different material from the adhesive properties standpoint.

4.2 SURFACE TREATMENT
4.2.1 CLEANING
Several cleaning procedures (acetone degreasing, alkaline etching, alkane etching+acid
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cleaning) were used before application epoxy coating on aluminum alloy. The surface
cleaning of aluminium alloy by alkaline etching followed by acid cleaning was the most
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efficient procedure for removing the oxide layer from aluminum. The surface roughness,
surface free energy, electrochemical activity, and adhesion strength of the epoxy coating to
the aluminum surface were significantly increased by this surface cleaning procedure
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(Figure 4.4). After alkaline etching, the intermetallic particles became more visible. Fur-