Metal corrosion and PH

[amin36]

Guys

Does low PH(below 7) cause corrosion to metals itself alone even when the CSI number is in the correct range or is it the CSI number getting below the recommanded level that causes metal corrosion?

Thanks

 

[Texas Splash]

Does low PH(below 7) cause corrosion to metals itself alone even when the CSI number is in the correct range

A low pH is the primary factor, although most times when the pH is that low (i.e. 6.8 and below) the CSI is also pulled down giving the impression CSI was the reason. But CSI determines how saturated the water is with calcium and how aggressive it may be to plaster products. Primarily a low pH is the reason for corrosion. See more good posts about this issue in the link below.

Negative CSI and metal corrosion

Split off of this topic. JasonLion Using Jason’s poolcalculator.com shows that your CSI is about a -0.70. A negative CSI means that the water is aggressive or tends to be corrosive. It can damage any mineral or metal based things like screws or ladders. A positive CSI means that the water...

www.troublefreepool.com

 

[SoDel]

I don’t know if this adds anything and if not, please ignore, but a mistake I made as recently as a few weeks ago was to conflate corrosive and caustic. Both low and high pH are bad for metals but are described differently and are independent of CSI. Low pH can give you metal corrosion and high pH can cause “caustic corrosion” at higher temps (like inside a heater). The upshot I guess is to the extent practical, keep an eye on both ends of the pH scale, not just low, and not just CSI, and follow the guidelines to prevent problems.

 

[amin36]

A low pH is the primary factor, although most times when the pH is that low (i.e. 6.8 and below) the CSI is also pulled down giving the impression CSI was the reason. But CSI determines how saturated the water is with calcium and how aggressive it may be to plaster products. Primarily a low pH is the reason for corrosion. See more good posts about this issue in the link below.

Negative CSI and metal corrosion

Split off of this topic. JasonLion Using Jason’s poolcalculator.com shows that your CSI is about a -0.70. A negative CSI means that the water is aggressive or tends to be corrosive. It can damage any mineral or metal based things like screws or ladders. A positive CSI means that the water...

www.troublefreepool.com

Thank you,very informative!

I don’t know if this adds anything and if not, please ignore, but a mistake I made as recently as a few weeks ago was to conflate corrosive and caustic. Both low and high pH are bad for metals but are described differently and are independent of CSI. Low pH can give you metal corrosion and high pH can cause “caustic corrosion” at higher temps (like inside a heater). The upshot I guess is to the extent practical, keep an eye on both ends of the pH scale, not just low, and not just CSI, and follow the guidelines to prevent problems.

Thanks alot