Unfortunately, the coil is made of steel.
And I noticed that the other screws are weak too, I don't know if Duralack will prevent corrosion completely.
As I searched the internet for thread repair, I came across special adhesives that are used when the thread is still holding a little. Maybe this could be the solution.
I understand that corrosion always occurred when you have two dissimilar metals, but you also need salt water. This are windows which are exposed to rain not salt water.