Sodium hexametaphosphate corrosion inhibitor is one of the commonly used water treatment corrosion inhibitor, which can inhibit metal corrosion on the surface of the equipment.
The adsorption mechanism of industrial sodium hexametaphosphate corrosion inhibitor means that the corrosion inhibitor has the adsorption effect on the metal surface, and the adsorption film adsorbed on the metal surface is formed, thereby producing the corrosion inhibition effect. Its main function is to form a protective film on the cathode through electrodeposition, and it has both corrosion and scale inhibition effects.
In order to make polyphosphate play a relatively low corrosion inhibition effect, the cooling water requires a certain amount of divalent metal ions, such as calcium, iron or zinc ions. It is not suitable to use polyphosphates as corrosion inhibitor in soft water with little calcium ions. In addition to the calcium content in the water has a great influence on the corrosion inhibition effect of polyphosphate, the dissolved oxygen content also affects the anticorrosion effect. This is because if the water does not contain dissolved oxygen, the polymeric phosphate in the water will form a soluble complex with iron to promote corrosion. Conversely, if there is a certain amount of dissolved oxygen, polymeric phosphate can form a protective film containing oxide. The molecular formula of sodium hexametaphosphate has only metaphosphate and no phosphate. After being dissolved in water and hydrolyzed, it will gradually hydrolyze into phosphate radicals, so six phosphate radicals will be produced after hydrolysis. Therefore, when selecting polyphosphates as corrosion inhibitors, meet the two requirements of calcium ion divalent metal and dissolved oxygen can obtain good results.