No sealant will defy mould forever, unless you dry it off after a shower. If you add up the time spent drying, it's normally less effort to replace the sealant every few years.
Dow Corning is without doubt the best silicon, It tends to last about ten years before deteriorating. The most important thing though, is to dry the mastic after use. Shower screens should be squeegeed and the silicon wiped over with an e-cloth. A real pain in the arse doing this after every shower but it does prolong the life of the sealant and prevents water stains on the shower screen.
Listen and learn.
There is a product called Muffycid. It will solve your problem. It costs about £8 a bottle.
Leave your old silicone where it is and spray this product on to it. The black mould will disappear like magic. You don't need to scrub or anything.
It is an anti fungicide and it sanitises the surface to prevent growth for some time. It is a miracle product and works on mould growth on wall paper too.
I am not a salesman for this product but had a problem at my home with an over used shower.
My local plumbers merchant stocks it and I have used it so many times without fail.
It's not the silicone that fails, it's bacteria that wins.
It's made by a company called Faren. Google it.
Jeff
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