Bleach and Fiberglass

[Muckle Flugga]

I am not a materials scientist, and have read a lot of salty threads and advice suggesting that bleach (and in this case I mean Sodium Hypochlorite, not the stuff that makes suicide blondes!) must not be used in the context of fiberglass.

However, on closer examination of this commonly held conviction, I have found significant quantities of the likes of this:

Corrosion Resistance Makes FRP Ideal for Handling Sodium Hypochlorite

https://plasticstoragetanks.com/sodi...rage_tanks.htm

It appears that professionals seem to use fiberglass as one of two primary means of storage of industrial quantities of concentrated sodium hypochlorite for extended periods.

So… can any actual materials scientists or other bright sparks who happen also to be boaties clarify the bleach on fiberglass question for me/us?

Does it depend upon the original composition of the fiberglass? Is this just another myth? Clarity would be appreciated!

[jwcolby54]

I love your tagline!

[Muckle Flugga]

Originally Posted by jwcolby54

I love your tagline!

Thanks matey. Enter it into Google in quotes and you will find out where it originated.

[jwcolby54]

and the scary part...

[thinwater]

Interesting question. I'm one of those guys that has specified FRP tanks to hold industrial bleach (15%). I have also done laundry bleaching tests on nylon and polyester lines in cooperation with rope manufactures.

• Nylon rope can be weakened about 10-15% if you soak repetitions for days in bleach concentrations 10x higher than anyone recommends. If you want to damage nylon rope, use strong acid (melts), power washer (obvious), or a washing machine (new rope can herniate, old rope can rip the agitator off if not bagged.
• Polyester rope was basically unaffected by bleach. A few percent. I did not test sail cloth or the resin.

So is using bleach on the deck for any reasonable period and any reasonable dosage going to hurt anything, other than remove the wax. Not hardly. In fact, bleach is unlikely to affect any synthetic material that is stable in the sun (if UV can't do it, neither can bleach).

That, said, bleach is quite alkaline and will attack aluminum and yellow metals quickly. Bad on bottom paint always and some other paints if exposed too long. There is always a "but."

By the same token, much of what bleach can "bleached" is already "bleached" by the sun. It is often not as effective as other cleaners.

[Muckle Flugga]

Originally Posted by thinwater

Interesting question. I'm one of those guys that has specified FRP tanks to hold industrial bleach (15%). I have also done laundry bleaching tests on nylon and polyester lines in cooperation with rope manufactures.

• Nylon rope can be weakened about 10-15% if you soak repetitions for days in bleach concentrations 10x higher than anyone recommends. If you want to damage nylon rope, use strong acid (melts), power washer (obvious), or a washing machine (new rope can herniate, old rope can rip the agitator off if not bagged.
• Polyester rope was basically unaffected by bleach. A few percent. I did not test sail cloth or the resin.

So is using bleach on the deck for any reasonable period and any reasonable dosage going to hurt anything, other than remove the wax. Not hardly. In fact, bleach is unlikely to affect any synthetic material that is stable in the sun (if UV can't do it, neither can bleach).

That, said, bleach is quite alkaline and will attack aluminum and yellow metals quickly. Bad on bottom paint always and some other paints if exposed too long. There is always a "but."

By the same token, much of what bleach can "bleached" is already "bleached" by the sun. It is often not as effective as other cleaners.

Thank you very much for your knowledgeable answer. May I request clarification for use of bleach in ungelled/uncoated fiberglass tanks (such as water tanks in some boats) or bilges, and other applications where the FRP of whatever stripe is not coated and is in direct contact (possibly for extended periods) with the NaClO? I have read a few supposedly knowledgeable threads in which contributors have suggested that prolonged FRP contact with "bleach" will soften it. About this I am skeptical but this is why I am seeking more expert opinion.

Would the same go for more or less any composition of cured resins within boat built FRP?