I know there has been a post about seals before with I think Tosh offering a solution,
Chris,
This wasn't me!
I've a few with oxidised frames, but haven't had any trouble with seals (apart from a couple of leaky windows).
Do you mean that when you scrim the edges of a window pane, the rubber sort of 'rubs off' and leaves a black mark on the PVC?
If so, I think these would be okay to WFP.
With oxidised frames or windows that leak, these are your options:
1. Do them using ladders and a squeegie.
2. Drop the account.
3. Miss the faulty windows out altogether.
4. Use your WFP, but avoid the problem areas of the windows and inform the customer they'll have to live with the results.
Depending on the account and the location of the window (ie if the window's position forced me to use my ladders in a dangerous manner; I'd use WFP; even though I have a good idea that it won't come up as well, because I'm avoiding the frames).
I use any of the above options depending on the circumstances. You just have to use a bit of judgement, common-sense, and have a 'have-a-go' attitude.
I do few accounts with oxidised frames and they come up really well with WFP. I know, because I've gotten my ladders off and checked them; nose to the glass.
I'd advise you not to go binning accounts before you've tried them a few times with WFP.
I also don't know whether you plan to do 100% WFP, or tops only. If you did do 100% WFP, I'd advise you to use a squeegie for the bottoms if the frames were oxidised, and explain to the customer that they'll have to live with the results for the 'tops'.
Explain it from a health & safety angle.