Corrosion inhibitor programmes for corrosion control.
Corrosion in petrochemical plants is an omnipresent thread. Many corrosive components are present in petrochemical process streams. Hydrogen sulfide (H2S), hydrochloric acid (HCl) or hydrofluoric acid (HF) can be present in petrochemical feedstocks. Gaseous HCl and H2S are soluble in water and may cause severe corrosion. The hydrogen sulfide solubility increases with an increasing pH and decreasing temperature. Carbon dioxide or low molecular weight organic acids can be present in condensates.
Caustic is often used as a neutraliser for corrosion control but has significant drawbacks. Caustic can cause stress corrosion cracking (caustic embrittlement). Sodium salts can deposit and may accelerate fouling and polymerisation. Corrosion is an electrochemical process. It can be controlled through the use of a chemical corrosion inhibitor programme. For corrosion control neutralising amines, filming amines or oxygen scavenger programmes are applied.
The neutraliser must provide good corrosion protection when the first acidic droplets condense. Criteria for a good neutralising amine programme are its amine and amine salt properties. The amines have to provide excellent initial condensate protection. A low salt deposition potential and good pH buffering are required. Kurita´s alkalising amines operate by reacting with any acid constituent in a straight forward reaction. The neutralising amine shifts the pH to a higher level, which improves the corrosion control. Our “ready-to-use formulations” provide the right combination of high-boiling and low-boiling amines. This ensures corrosion control in the steam and water phase.
Small amounts of oxygen accelerate corrosion when water condensation occurs. The metal surface reacts with oxygen by forming ferric hydroxide. The reaction product is insoluble in water and will precipitate. Corrosion by oxygen can be controlled with an oxygen scavenger. Oxygen corrosion is frequently observed in boilers or dilution steam generator systems (DSG). For many years hydrazine was used as a corrosion inhibitor. It is no longer allowed to be used in many countries being carcinogenic. Kurita´s very effective oxygen scavenger programmes are easy to handle. Our oxygen scavenger products are not carcinogenic in order to protect and maintain the health of the employees.
Kurita´s corrosion inhibitor filming programmes can help to stop or decelerate the corrosion. They will provide perfect protection by forming a very thin film. The film acts as a barrier against corrosive substances. If filming amines are selected, oxygen scavengers, phosphates and caustic dispersants are no longer required. The filming amines can be used in combination with alkalising amines.
We apply sodium-free corrosion inhibitor products. This avoids sodium-induced stress corrosion cracking and the formation of coke in the steam cracker. Dangerous amalgam corrosion in the raw gas flow is inhibited by the use of our special mercury scavengers.
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