Hispano-Suiza water pump - Al Alloy - First World War

Granget. Elodie (, None) & . (MNAM (Musée National de l'Automobile de Mulhouse), Mulhouse, Alsace, France)

Complementary information

This engine part was given to the MNAM as reference material for a study on aluminium corrosion in engine cooling systems. Neither the model of the car nore the full context of use and conservation are known.

The schematic representation below gives an overview of the corrosion layers encountered on the object from a first visual macroscopic observation

Fig.1: Stratigraphic representation1 of the water pump in cross-section using the MiCorr
Fig.2: Stratigraphic representation 2 of the water pump in cross-section using the MiCorr

XRF-EDS analysis with Niton® XL3t [Thermo Fisher Scientific]: General Metals Mode

Voltage: 50V

Energy Max: 50KeV

Anode: Silver

MAIN RANGE (no filter)30 sec

LOW RANGE (filter Cu)15 sec

LIGHT RANGE (filter Ti)15 sec

No metallography has been done on this piece yet. 

The alloy has been identified as  Al88.3 Si10.1 Cu0.8 Fe0.6 Zn0.1 Pb0.1 using XRF-EDS.

La faible teneur en Cu me semble bizarre aux vues des produits de corrosion. Je ne sais pas sur quelle partie du pas pris la mesure XRF. A posteriori je me dis qu'il est possible que deux alliages aient été utilisés. Une Al-Si pour le corps (là où je pense que tu as fait la mesure) et un Al-Cu pour la fixation, qui est maintenant très corrodé. Ceci pourra être vérifié, la pièce pourrait être envoyée en Suisse.

The metal is slightly porous and the surface is imperfect, as one can expect from a functionnal cast piece.

Complementary information

This is an hypothetical structure based on the manufacturing technique used to create this engine part

This part of the pump is so heavily corroded, the exit pipe is now missing. 

One can recognize products of Copper (from the alloy) and Iron (probably from the steel screws nearby) imbeded in the Aluminium corrosion.

The white layers of corrosion are more powdery than the ones charged with Fe or Cu products. The metal has been completely consumed, following the dendritic microstructure of the alloy.

 

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Pas très détaillé les "corrosion type" pour l'Aluminium. Je ne sais que mettre et ne peux pas insérer de nouvelles formes

This is a case of transgranular corrosion combine with erosion corrosion caused by the water propulsed by the turbine against the exit pipe.