I'd like to use my Scotts sprayer for etching my basement walls prior to waterproofing. Will Muriatic Acid ruin he plastic container / rubber hoses?

I'd be concerned using it indoors. Particularly in any volume due to lack of serious ventilation. Muriatic acid is another name for hydrochloric acid. It's pretty harsh stuff. If it hurts the garden sprayer should be the least of the concerns.

A breathing mask specifically rated for Hydrochloric acid is a MUST.

Hell NO! Are you trying to kill yourself?

Review these links carefully

How to Acid Wash Concrete: 12 Steps (with Pictures) - wikiHow

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Muriatic acid (hydrochloric acid) is the most dangerous option and produces strong fumes. Recommended only for professionals working outdoors.

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Not really recommended for a first time do it yourselfer!

How to Acid Etch Concrete (with Pictures) - wikiHow

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Other suitable acids for etching include phosphoric acid and sulfamic acid. The latter is an especially good choice for first-timers because it is much less caustic and dangerous than the other acids.

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I'm glad I asked. I saw a post from 2008 indicating etching with Muriatic Acid was a must... https://www.askmehelpdesk.com/interior-home-improvement/drylock-product-comparison-170035.html#post3800967

I've finished off a few basements in past, but never used the stuff. I've always used Bleach and a scrub brush to clean the walls prior to waterproofing (using goggles, gloves and a mask as well). This approach worked fine for me on 3 other basements in the past 30 years, so unless you have any other advice I think I'll stick with it.