[sdiy] Solder corrosion - what is it? [hijack]

[MTG]

On 11/4/2016 3:39 AM, Steve Lenham wrote:
>
> Neither water nor IPA dissolve the corrosion significantly. The only way
> to get back to a shiny tinned surface is with slight abrasion e.g. a
> fibreglass pencil, etc.

I've never ever heard of a fibreglass pencil before, but it looks 
interesting. Is this helpful in removing soldermask? I have some 
instances where I have to clear the solder mask off of a ground fill or 
whatever to add a wire and a Xacto knife is not really helping much.

GB