Black on Rivet Head After Riveting

I am just getting around to asking about this issue. Has anyone else noticed the manufactured head turning black, after riveting? The 2nd rivet from the left shows darker than the others in this picture...



Can someone enlighten me as to what this is? What causes it? Should I be worried? Just ignore it? It clearly does not happen every time, as the 1st and 3rd rivets are clean. The 4th is showing some darkness again.

I forgot to take a picture of my mushroom set, but it definitely is sparkling clean.

jae

Hi Jae,

I wouldn't worry about it. Happens sometimes - I presume from the mushroom set 'polishing' the head a bit.

No worries but if you use a piece of masking tape you will not get this, I have not used tape on my 426 rivets but I always use it on the 470s and when your done they look just like when you slide them in.

The color on the rivet head is AL oxide. Clean your tools with AL polish before you rivet and you will not get the black color.

KM

N282RV said:

No worries but if you use a piece of masking tape you will not get this, I have not used tape on my 426 rivets but I always use it on the 470s and when your done they look just like when you slide them in.

Click to expand...

I concur, although if you do use making tape or some sort of other tape, set it in your mind that you will --without fail -- remove it and change it every few rivets. Sometimes that tape can get under the rivet head if you move the gun and that's just plain no fun at all.

Thanks guys

Thanks for the input. My main concern was for any structural issues. Cosmetically, it's fairly minor, except for my trailing edges. When using the flush set on the trailing edge of my rudder, i got the black smudging on the actual alclad itself, which was a bit unnerving.

Thanks again!
Jae