Coke quenching water

[corrosionman]

During the production process red hot coke is instantaneously cooled by quenching with water (200 tons in 10 minutes) The water recirculates - - - it achieves a steady 70 degree cent and is held in an unlined steel tank which has lost 8 mm thickness in 8 years. Please has anyone any expeience of whats happening here - - will the water be acidic or what, and will the reduction in tank wall thickness be due to corrosion or to erosion by the coke dust which recirculates in the water? ( I am told the water has pH of 8.0 ) Any comments much appreciated.
Corrosionman.

 

[cloa]

pH 8.0 is slightly caustic- not acidic

 

[whammett]

You might want to consider sampling on a daily basis and use a dosing pump as needed to add an acid to control pH. pH tests are relatively inevpensive, if you don't feel like shelling out a little more money for a pH analyzer.

"Scientists dream about doing great things. Engineers do them." -James Michener

 

[Compositepro]

Carbon in contact with iron will lead to severe galvanic corrosion in the presence of an electrolyte.

 

[KENAT]

Also, if there's sediment in the water and a reasonable flow rate there might be abrasion. Or if the sediment is cleaned out of the tank maybe this causes abrasion.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[strider6]

is the water deoxygenated?

S

Corrosion & Rust Prevention Control

 

[corrosionman]

Gentlemen all your comments are so helpfull and have just about given the answer. Compositepro ,I think yours is the key suggestion. We have a very good understanding of galvanic corrosion but somehow never realised that wet coke is so very "powerfull". Into a saucer of tapwater we put a piece of mild steel and a piece of coke - - The voltage between them is 0.61 volts ( For Mild steel and stainless steel it is only 0.3 volts). The quench water tank floor will have coke sediment on it which just "eats" away at the mild steel, and recirculation of quench water every hour keeps things moving. I think we are beginning to understand the problem and how to protect a new tank (Rubber lining).
This is such a usefull forum
Many thanks
Corrosionman.

 

[Compositepro]

Yes,the dust from machining carbon fiber composites can quickly destroy machine tools if water is used for the coolant. Salts in the water and oxygen are part of the mechanism.