Remove solid scale which is formed from CaCO3 or BaSO4

[hyemi]

Hi,

Does anyone know how to remove solid scale which is formed from CaCO3 or BaSO4?

 

[bimr]

Hydrochloric acid among other acids will easily remove the scale. Having said that, the acid is hazardous to use and may damage the substrate that has scaled.

 

[zdas04]

"Easily" is pretty subjective.

CaCO3 will dissolve in mild acid (something like vinegar with a pH of around 4.5 or acetic acid (pH around 2.4) without having to go to really nasty stuff.

Barium sulfate is a bigger deal. It will dissolve in hydrochloric acid (pH 0.1), but not quickly.

I've had more predictable results with these phase change scales by using hydroflouric acid (pH around 3.1) and I'm not certain why it seems to fix the problem faster than the much stronger acids we use. I found it by trying to find ways to get rid of Nacholite (NaCO3) which is just about as hard and shinny as granite. The aggressive acids would spend themselves before getting it out of the way. Hydroflouric acid would get rid of it faster with less iron loss. I've never used it on pure BaSO4, but I'd certainly try it before filling my pipe with HCl.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[MortenA]

David, under what circumstance do you experience NaCO3? Was this in the matrix or in tubing/pipes?

 

[MortenA]

Normally i wouldnt dream of making fun of a spelling error - but i assume that Nacholite is not a tex-mex version of Nahcolite

 

[zdas04]

I messed that up a lot. Nahcolite (NaHCO3, not NaCO3) is what I meant. I was in a hurry. I love the peer-review on this site.

I've found it in downhole in well tubing, on separator mist pads, and inside (never outside) control valves. It seems to be most common at a pH around 7.2-7.6 with Sodium and Chloride both less than about 3,000 mg/L and the primary buffer being bicarbonate. Even in that environment, if the phase-change is kind of slow (e.g., thread or packing leaks on control valves) the salt tends to be NaCl instead of NaHCO3. This seems really backwards to me (Nahcolite is really hard, dense, and shiny, and NaCl is really crumbly, porous, and dull, seems like quick formation would drive towards the fluffy stuff, but it doesn't seem to).

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[bimr]

Nahcolite formation requires high CO2 concentrations. As Nahcolite forms, the CO2 is removed from solution.

Hydrofluoric Acid is one of the most dangerous acids known. It is so potent that contact with it may not even be noticed until long after serious damage has been done. Even very strong acids do not have the power to cause death and injury in the way that Hydrofluoric Acid can.

 

[HEC]

Hyemi,
what is pipe material you are trying to remove the scale from and what is the fluid in the pipe? I have had variable success using brush pigs for removal of Jarrosite from mineral liquour lines. Low pH and lots of free iron.
Zdas04
Used hydrofluric acid for pickle passivate stainless steel systems long ago. The paranoia and disposal issues wihgt the app;lication convinced me to never use it again!
Cheers
Mark hutton

Mark Hutton