Internal porosities
Located at the heart of the material, they do not emerge on the surface until any machining cuts them. However, they can become exposed during drilling, tapping or surfacing.
Foundry defects
Porosities of metal parts
Understand the origin of porosities, their consequences on waterproofing and why impregnation constitutes the most reliable industrial response.
Porosities are inherent to foundry and metallurgy processes. They arise during the solidification of the metal and appear in the form of more or less interconnected cavities.
They can remain invisible until machining or leak testing operations. This is why impregnation is often planned during the design of the most critical parts.
Main causes of porosity
- Unfavorable casting conditions (temperature, speed, turbulence)
- Gases dissolved in liquid metal
- Shrinkage linked to volume variations during solidification
- Presence of inclusions or nuclei difficult to degas
- Part design generating thermal concentration zones
3
families
typical porosities
10-6
bars
Targeted waterproofing after impregnation
The same part can have several types of porosity, hence the need for global treatment.
Porosity categories
Beyond the surface appearance, it is the way in which the porosities communicate with each other and with the outside which will determine the actual tightness of the part.
Surface porosities
Visible or not to the naked eye, they disrupt the appearance, the durability of the coatings or even the resistance to corrosion (pinholes, pits, blowholes, etc.).
How to detect porosity?
Before considering impregnation, it is necessary to qualify the type of defect encountered. Maldaner can support this diagnostic stage.
- Air/air or air/water tightness check on raw or machined part
- Observation of bleeding or seeping after pressurization
- Analysis of rejects during final inspection (bench leaks, functional leaks)
- Foundry coupons and metallographic sections to analyze the structure
Why treat porosities by impregnation?
Recover non-compliant parts
Upgrading porous parts without rejecting them, while maintaining their mechanical performance and dimensions.
Secure critical functions
Avoid fluid leaks (oils, coolants, gases) into hydraulic, pneumatic or thermal components.
Control your costs
Limit the risks of field returns, warranty breakages and material scrap, while stabilizing your first pass rates.
Do you want to analyze a case of porosity on your parts?
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Find out why impregnation has become an essential operation and how the Maldaner process works.