Die Casting Porosity: Causes, Prevention and Buyer Inspection Notes

2026-06-17 11:15:42

Porosity is one of the most discussed defects in die casting because it can affect strength, sealing, machining and appearance. It is also often misunderstood. Not every pore has the same cause or the same risk.

What the defect usually means

Porosity can come from trapped air, shrinkage, poor venting, heavy wall sections or process instability. The control method depends on the part design and functional requirement.

Common causes and practical prevention

What buyers can do before tooling

Buyers should identify whether porosity is cosmetic, structural or sealing-related. A hidden pore in a non-critical area may be acceptable, while porosity on a machined sealing face may not be.

How inspection should be connected to the risk

Inspection can include visual checks, machining surface review, leak testing for sealing parts, or section analysis for critical projects. The inspection method should match the risk.

Practical RFQ note

Send information about pressure, sealing, machining depth and load requirement so the supplier can judge porosity risk before tooling.

Related reference: aluminum die casting cylindrical housing component and Die Casting Process Control.

Porosity should be classified before it is blamed

Porosity is not one single problem. Gas porosity, shrinkage porosity and exposed voids after machining may require different corrections. The most useful supplier discussion is not "can you guarantee zero porosity", but "where is porosity unacceptable and how will those areas be controlled". This is especially important around sealing faces, threaded holes, pressure zones and cosmetic surfaces.

What buyers can specify

Mark no-porosity zones on the drawing if the part has sealing or pressure requirements. For ordinary covers and brackets, define appearance and functional acceptance instead of using a broad requirement that is impossible to inspect consistently.