Capillary Action
Capillary action is the rise or penetration of liquids into narrow gaps due to surface tension and wetting ability. This can lead to porosity if the liquid does not dry out completely.
Physical-Chemical Mechanism of Action
Capillary action occurs due to surface tension and the wetting ability of liquids in narrow gaps or cracks. The surface tension attracts the liquid, causing it to move upward on its own.
Metallurgical Relevance & Welding Risks
During welding, water or other liquids can penetrate narrow gaps or cracks and rise. This leads to porosity, which impairs the strength and toughness of the weld. Porosity can also cause hot cracking and corrosion.
Workshop Practice & Action Instructions
To minimize capillary action, during welding:
• The weld surface should be cleaned to remove narrow gaps or cracks.
• The weld pool should be well covered and protected to keep water and other liquids away from the area.
• Cooling should be controlled to prevent the formation of porosity.