# 4.3.3 Surface Preparation: Mechanical Abrasion and Roughening

> From: LOCTITE®X Digital Manual for Bonding (https://www.loctitex.com/en/manuals/bonding/4.3.3-surface-preparation-mechanical-abrasion-and-roughening/)

#### 4.3.3 Surface Preparation: Mechanical Abrasion and Roughening

Increased bond strength is a beneficial side effect of cleaning by mechanical abrasion. Substrate surfaces are frequently roughened to take advantage of this, regardless of any cleaning requirements.

_Figure 88 Corroded steel, prepared by grit blasting_

![Figure 88 Corroded steel, prepared by grit blasting](/en/manuals/bonding/assets/img/cleaning-surface-preparation-corroded-substrate.jpg)

![Figure 88 Corroded steel, prepared by grit blasting](/en/manuals/bonding/assets/img/cleaning-surface-preparation-cleaned-gritblast-substrate.jpg)

Roughening a surface increases bond strength in two ways. The roughened surface presents a larger bond area and adhesive, which flows into microscopic cracks and porosity of the surface, cures solid and mechanically locks into the surface.

The beneficial effect of roughening substrates is measurable, as shown in Table 14.

_Table 14 Butt joint tensile strengths with abraded aluminium substrates and an epoxy adhesive. From C.W. Jennings 1972_

Adherend Surface Treatment Tensile Strength N/mm2 (psi) Strength Difference from Polished Surface Finish Polished, 1 µ diamond dust 28.8 ± 7.0 (4,180 ± 1,020) n/a Abraded Through 600 paper 30.9 ± 7.7 (4,480 ± 1,120) + 7.2% Abraded Through 280 paper 39.0 ± 6.8 (5,660 ± 0,990) + 35.4% Abraded Through 180 paper 36.7 ± 7.5 (5,320 ± 1,090) + 27.3% Sandblasted (40-50 grit) 48.5 ± 7.0 (7,030 ± 1,020) + 68.2%

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