How quickly does scale or etching occur!

[eqbob]

So if I measured my chemistry 2 days ago and we were balanced including LSI and CSI...and then today I measured again and pH was a wee high at 8 with 1 drop needed to bring it down to 7.6, so 9 ounces of MA was added. Tested again a few hours later and everything is nailed on the chemistry.

So how long does something have to be 'off' before the pool starts being subject to scaling or corrosion? 1 hour and the process starts? 1 day? 1 week?

Not a panic question...a curiosity question.

 

[eqbob]

Does anyone have a thought on this? ChemGeek?

 

[chem geek]

It's not so much the time as the degree away from balanced CSI and also another factor which is the capacity for change known as the Calcium Carbonate Precipitate Potential (CCPP). Generally, we don't see scaling in pools until the CSI gets to at least +0.7 and especially +1.0 or higher. In hot spas, scaling can sometimes be seen when the CSI is +0.3 or higher. If the CSI gets high to +1.0 or more then scaling could occur in hours but to get a substantial amount of scaling usually requires sustained high CSI over many days. It really depends on how high the CSI gets how quickly.

As for degradation of plaster, this is usually much slower unless the pH is low. Degradation usually takes months if not years, but again that depends a lot on the pH. It also depends on the quality of the plaster and if it is finished curing. Plaster is most susceptible to dissolving shortly after it has been freshly made and in the weeks after, but after a month or so it should be more resistant, but again depends on how well the plaster was made. Plaster higher in calcium chloride content will be weaker and more susceptible. If you pour strong acid directly onto plaster, it can degrade in seconds to minutes.

 

[eqbob]

Thank you. You've given me a better understanding of the timeframes and parameter ranges. I appreciate it.