Is this corrosion?

[djohns]

Is this corrosion or just an impurity in the aluminum? I have scuffed with the maroon Scotch-Brite pad but would need to do a considerable bit more to remove it.

 

[dwollen89]

Scott, Larry and others are much more of an authority on things like this, but it doesn't look like it to me. Most of the corrosion that I've seen is the filiform (sp?) corrosion which presents almost like small white snow flakes. It's easy to remove with a scotchbrite pad.

To me this looks like possibly being from the laser cutting the holes.

 

[Freemasm]

Deceiving picture? Appears to be raised -> deposit, slag, etc though from what I have no idea. Can you catch it with a fingernail or straight edge. Just curious.

Oxide would be softer than the parent metal. Can you discern with a pick?

 

[fixnflyguy]

Yep

Looks like corrosion, smells like corrosion, probably tastes like it too. Very typical to start at a fastener hole, or edge. That's where the Alclad is breached. I don't recognize the part, but you'll have to blend it out for sure if you want it gone.

 

[Zero4Zulu]

It looks like it’s from the laser cutting. Slag or splatter.

 

[djohns]

Deceiving picture? Appears to be raised -> deposit, slag, etc though from what I have no idea. Can you catch it with a fingernail or straight edge. Just curious.

Oxide would be softer than the parent metal. Can you discern with a pick?

It is raised. I have also seen areas with a brown haze around holes. Probably part of the laser cutting process too. Very easy to clean almost with just your finger.

 

[Tlrguy]

Yep, laser cut part and that is slag from the process. Hit it with your scotchbrite wheel and carry on.

 

[VA Maule]

From the OP’s tag lines it appears that he’s building a 14 and I believe that they have the final size laser cut holes. As noted in some other recent posts the laser processes leaves notched starting spots just like what’s showing in the close up picture. So my suspicion is it’s splatter from the laser cutting.

Try dressing the splatter ( questionable corrosion) with a file and see if it produces shavings . If it makes shavings it’s splatter if what you file off turns into dust and sort disappears when rubbed between your fingers it’s corrosion.