Effect of Low pH water on carbon steel Pipe

A. I am not an expert! You may get by on long runs of straight pipe if it forms enough of a rust / slime barrier to protect the pipe. I would expect a more rapid failure of welded or threaded joints, elbows and areas of high velocity or turbulent flow. The higher the temperature, the faster the attack will be. It surely does not sound like a good choice.

A. Mr. Zobeir,

There is a method of lining the pipe with a sprayable thermoplastic coating, the basic method is to heat the pipe and then spray it in when the pipe is hot. The pipe needs to be on something that will spin it during the spraying to make sure that the coating is uniform. It will have to be holiday tested afterward to make sure that there is total coverage, but you'll need to do some research to get more detail as my knowledge is limited. Something that you didn't mention was what the pipe is used for. If it is going to be used as a drainage pipe for chemical tanks, all you have to do is adjust the ph of the tank so that it is neutral before draining it.

A. Mr.Zobeir,

I'll try to give you some possibilities to answer your concern.

1. "...if there is any sort of corrosion expected due to low pH in water (4.0 to 5.0)..."

yes,there will be a high potential of internal corrosion damage on your pipe, but the severity depends on the type of fluid you running. The severity can be increased by:
- operational temperature,
- gases (CO2, H2S, O2) solubility in the water,
- salt type and concentration, for example if your water contains an adequate concentration of Ca++, then the possibility is you will having scaling problem (you can see pages about Ryznar & Langelier Index for this kind of trouble), but if not, then usually it will be general and/or some localized corrosion (and this will be bad),
- fluid velocity (for this reason you can see API RP-14E),
- bacteria activity, but usually exist in sulfur rich media), and
- solid particles (i.e: sand) that carried away in your system.

2. "...what is the available methods for pipe corrosion protection."

for new uninstalled pipe perhaps you can do what Mr.Taylor suggest, but if its already installed, you can try using corrosion or scaling inhibitors (there should be many of them), and if you use inhibitor,perhaps you can consider installing corrosion monitoring equipments also to, well, monitor the corrosion activity inside your pipe and adjust the amount of inhibitor you are using. The less expensive and simplest of this method is by installing corrosion coupon or scale coupons,

I hope this will answer your question, and good luck!