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My cat has a habit of urinating in the bathroom sink. It is unsanitary, but can it corrode the stainless steel plumbing hardware? My friend believes it will, but I disagree. I could believe that if the urine were left to sit over time it could possibly affect the electropolished layer, but it is generally cleaned up within 24 hours.

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  • $\begingroup$ You do not have a stainless steel sink drain. It is 70:30 cartridge brass with nickle/chrome plating ( or equal; admiralty metal , muntz metal, etc) . $\endgroup$ – blacksmith37 Sep 2 '17 at 11:18
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Well, infact yes, cat urine can corrode stainless steel plumbing.

Urine of any mammals contains quite a lot of ions, and the chloride ion concentration is quite high. Chlorides attack the passive layer of steel, exposing the reactive iron underneath.

Pitting corrosion - The passive layer on stainless steel can be attacked by certain chemical species. The chloride ion Cl- is the most common of these and is found in everyday materials such as salt and bleach. Pitting corrosion is avoided by making sure that stainless steel does not come into prolonged contact with harmful chemicals or by choosing a grade of steel which is more resistant to attack. The pitting corrosion resistance can be assessed using the Pitting Resistance Equivalent Number calculated from the alloy content.[1]

While you may clean up the urine quickly, if your cat does this frequently, it can add up to corrosion very quickly. I'd suggest doing whatever you can to make your cat from urinating in the sink.


  1. “BRITISH STAINLESS STEEL ASSOCIATION Making the Most of Stainless Steel.” What Forms of Corrosion Can Occur in Stainless Steels?, www.bssa.org.uk/faq.php?id=9.
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I would be surprised if you have stainless plumbing ( cost >>> brass ). Any urine produces ammonia. Ammonia causes stress corrosion cracking in any brass and some other copper alloys. In the UK it may be called "season cracking" ( for the rain season in India ). So, if you have brass , I would keep it rinsed. Urine would most likely cause only cosmetic damage to stainless. These factors ( cracking of brass - no problem for stainless) have resulted in the flex tubing for connecting gas home appliances being made of stainless today when 30 + years ago they were brass. Footnote : Years ago, I had a gas space heater in a garage , a dog urinated on the brass flex tube and it cracked and leaked .

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