Problems With Flash Rust on Castings After Blasting?

May 22 2014, by Transmet Corp in Application Bulletins

Flash Rust on Castings

Shot blasting of aluminum castings with steel shot can leave parts looking dull and dirty. Steel shot residue trapped on parts can also cause flash rust on castings. This leaves your castings with freckles of rust on the surface and in casting crevices. In periods of high humidity these freckles can appear overnight as the casting moves through subsequent machining, painting, or assembly steps.

 

Transmet Blast Media

Customers that have switched to Transmet Cast Aluminum Shot or Cast Zinc Shot have reported lower show usage, lower freight expense, lower inventory cost, and less dust produced and recycled.

Shot blasting with Cast Aluminum Shot leaves a brighter finish than steel:

 

Aluminum Casting Blasted With Steel Shot, Leaving Surface Dull and Dirty

Before: Aluminum Casting Blasted With Steel Shot

Bright Aluminum Casting After Shot Blasting With Cast Aluminum Shot

After: Aluminum Casting Blasted With Cast Aluminum Shot

 

Cast Zinc Shot has the mass for flash removal and deburring, leaving a brighter surface finish:

 

Flash Rust on Castings: Iron Wrench Before Blasting With Cast Zinc Shot

Before: Rusty Cast Iron Wrench

Cast Iron Wrench Blasted With Cast Zinc Shot Blast Media

After: Same Cast Iron Wrench Blasted With Cast Zinc Shot

 

Blasting cast iron or other ferrous materials with Cast Zinc Shot leaves a 1-micron thick coating to temporarily prevent flash rust.

 

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