What is the impact of increasing salinity on the effectiveness of filming amine corrosion inhibitors?

Increasing salinity generally reduces the effectiveness of filming amine corrosion inhibitors. Filming amines are a class of corrosion inhibitors that work by adsorbing onto metal surfaces to form a hydrophobic (water-repelling) film, which acts as a barrier to prevent corrosive agents from reaching the metal. The effectiveness of this film depends on several factors, including the concentration of the inhibitor, the temperature, the flow rate, and the salinity of the water. Salinity refers to the concentration of dissolved salts, primarily sodium chloride (NaCl), in the water. Increased salinity can interfere with the adsorption of the filming amine onto the metal surface. The high concentration of ions (Na+ and Cl-) in saline water competes with the filming amine for adsorption sites on the metal. This is because the metal surface can also attract these ions, reducing the number of sites available for the filming amine to bind. Additionally, high salinity can increase the conductivity of the water, which can promote electrochemical corrosion. The increased ionic strength of the water can also weaken the film formed by the filming amine, making it more susceptible to disruption by flow or mechanical forces. Some salts present at higher concentrations, like calcium or magnesium chlorides, can react with some filming amines, causing them to precipitate out of solution and reducing the available inhibitor concentration. Therefore, in high-salinity environments, higher concentrations of filming amine inhibitors may be required to achieve the same level of corrosion protection as in low-salinity environments. The specific impact of salinity depends on the type of filming amine used and the specific composition of the saline water.