Pinholes in aluminum siding skin under roofline

[Yamaha314]

Was washing my toy hauler and notice what at first looked like dirt spots above the rear bunk window. Found to be very small pinholes in the siding! pushed around them with my finger and squeezed water out (just washed it).
I don't know if the water got in while washing, or if my roof or gutter seam leaked it in, but either way, I am wondering what has caused the holes to develop in aluminum skin????? I think my hauler has skin cancer!!!!! I am now so paranoid about the roof leaking / skylight issues / wet walls that I just spent 11K on a huge carport to keep it inside and am now only wanting to use the thing in sunny weather!!!

[clutch]

I don't think that water would cause the pin holes you are talking about. The top sheet of siding should come off and check for problems. Probably not something to be attempted at home.

[3'senough]

Did the pin holes have a blister type bump over them that crumbled when you ran your finger over them? Should look somewhat calsified or whitish in color under the paint. If so then you are most likely having some corrosion type issues pertainng to salt or other compound that is reacting with your "skin". Those will only grow since you now have bare aluminum exposed in the areas so it needs to be addressed. More importantly your entire skin should be evaluated for more of this type corrosion.

I've seen it happen mostly on aluminum boats where salt water gets under the finish.

[Lady Fitzgerald]

Under certain conditions, aluminum can corrode, even without sea water present. I'm guessing (note that I said guessing) that the pinholes are the first visual sign of "skin cancer" (as you so aptly put it). I'm guessing (again) you have/had a roof leak that let water get trapped between the wood of the framing and the skin, causing wood rot which probably caused corrosion of the aluminum. The only way you will be able to accurately determine the extent of the damage is to remove the siding to see how bad the damage to the inside of the siding is and if you have any wood rot going on.