Photo 1 illustrates a cast A360 aluminum part (an alloy that has a good rating for corrosion resistance) showing signs of severe corrosion over many areas after 30 days of salt spray testing.
In a high magnification shown in photo 2, the same A360 casting exhibits severe signs of corrosion on the corners (which have been rounded). In addition the casting surface shows signs of surface degradation.
After removing the top cover( Photo3) the surface of the A360 casting, which contained a pour in place gasket, exhibits signs of water intrusion leading to product failure. Corrosion to the edge of the casting was pronounced. The raised area on the perimeter of the casting showed signs of aggressive corrosion. This casting had indications of water around the entire sealing surface. Surface pitting was visible on all casting surfaces.
To clarify the corrosion damage the above A360 casting was lightly bead blasted to remove the adhesive and aluminum oxide from the sealing surface. Photo 4 clearly shows that the aluminum material had been removed by the salt spray process. Pitting on the casting surface was uniform across the casting. The raised perimeter was completely missing in some places.
Photo 6 is a housing manufactured from Delphi K-Alloy. This
casting was exposed to the same 30-day salt spray cycle as
above. Pronounced deterioration of the screw fasteners is
evident from the white ring around the contact point on the
casting. The casting itself did not show signs of
corrosion.
Photo 7 is the same K-Alloy casting as Photo 6 with the top
lid removed. The sealed surface was still intact and showed
no sign of water intrusion. The housing showed no sign of
surface corrosion.
Photo 8 is the same K-Alloy casting as Photo 6 after is had
been lightly blasted with glass beads to remove salt
residue and dispensed adhesive material on the sealing
surface. The casting shows no visual damage from corrosion
or metal loss due to salt spray reaction.
