Corrosion

Is there a solution to repair this?

WTF? That looks like a lighting strike. Is that a European all-aluminum mast?

Short answer is no - but damage like that is probably cosmetic.

It is a combitip mast.

I would grind out/knock off any loose corrosion and then mix up a batch of thickened epoxy resin or marine tex and fill it in. Wrap a piece of packing tape over it to force the epoxy to contour to the mast. At least that way it is sealed to prevent exposure to salt water. I would also pull off the mast tang to make sure the mast looks clean under the tang.

It might even be worth pulling off the comptip and inspecting from the inside. I wonder if salt water migrated in between the comptip/aluminum mast joint and caused it to corrode from the inside out. If that is the case, there could be additional unseen damage on the inside of the mast.

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I just had one like that but it started from the inside right where the foam waterstop is located (yes it went all the way thru the mast so I could see the foam).
I cleaned it out and used JB weld to "fill" the hole. stronger and closer to the mast color than marine tex.

I'm just getting started on repairing an old 17 someone gave me.

If the damage is also further down the (inside) of the mast it might be helpful to use another mast fitting. I think the H16 has extrat fixing points that help with the jib loads.

I'm still sitting on a perfectly good H17 mast & tip. The trouble is shipping costs from Oz to US is just too high to make sense.

To the Netherlands would be even more expensive.......