Mouldy mdf

I have some mdf that I am going to paint white. It was stored in the carport for a year and perhaps as a result of some damp, it has spots of what looks like mould on the surface.

Should I just paint over the top or should I put some anti-mould treatment on before undercoating? I assume yes, but wanted some thoughts from you guys in case I am being too fussy.

Any recommendations?

TIA

Get rid of it Jeremy once damp has got into MDF its gone and mould will eat it to bits, regardless of anti mould paint.

I tend to agree with Wheelin' Jeremy. If it got wet enough to go moldy it is probably defunct as serious building material. even modest amounts of water start the stuff on the road to delamination - it really is thick cardboard - I chucked the bits I had that had gone that path, it really did look like a bunch of identical paper cutouts :doh:

That said, if you were going to use it for something with a limited life expectancy, I'd recommend getting the strongest mold killer you can find - the down side of that is that almost all of them are going to be water based - see paragraph 1. Paint will not last on a moldy surface - Dad was a painter for most of his life & always washed down every outside job (plus bathrooms & laundries etc) with neat chlorine bleach to kill the mold spores - he only had to go back & fix one job that I know of - he had used a commercial mold killer & adhesion additive that failed miserably.

black spots on MDF shows it up to be exactly what it is,.... worthless.Throw it and start again with anything else

Thanks all for the responses, especially Bruce.

I perhaps should have made it clear that the mdf is a 3mm facing on blockboard which is just there to provide a good paintable surface, and the mould is clearly pretty minor at the moment and does not affect the structural integrity of the sheet.

Also, the project itself is strictly utilitarian (bookshelves for my study) and is to be painted white, so to use anything more "beautiful" would be a waste of good wood!

So with Bruce's dad's advice in my ear I went off to Bunnies and found that Flood (the people who make ESP) have a pre-paint mould preparation called Mould Action. So a bottle of that was purchased and the preparation was brushed onto the mdf surfaces last night.

The good news is that the mould has been dramatically reduced overnight withonly a couple of spots requiring reapplication.

So fa, so good. I'll let you know if the mouold comes back after the painting.