Defoamer reaction after stirring
At present, in addition to the use of cathodic protection and corrosion inhibitors to provide anti-corrosion protection for oil pipes, coatings are gradually accepted by people due to their economy and effectiveness, and have become one of the effective ways to prevent pipe corrosion. Since bubbles are easily generated during the mixing, construction and curing process of the coating, if the bubbles cannot be removed, they will remain in the coating after curing and become defects, thus providing a channel for the entry of corrosive media. At present, there are many studies on defoamers, most of which start from the defoaming mechanism and the influence of defoamers on the construction performance of coatings. There are still few literatures that consider the defoaming effect of defoamers from the perspective of corrosion.
1. The reduction of the surface tension of the foam part leads to the collapse of the foam
The source of this mechanism is that higher alcohols or vegetable oils are sprinkled on the foam. When they are dissolved in the foam liquid, the surface tension of the place will be significantly reduced. Since these substances are generally less soluble in water, the reduction of surface tension is limited to the foam part, and the surface tension around the foam is almost unchanged. The part with reduced surface tension is violently pulled and extended to the surrounding area, and finally breaks.
2. Defoamers can destroy the elasticity of the membrane and cause bubbles to collapse
When defoamers are added to the foam system, they will diffuse to the gas-liquid interface, making it difficult for the surfactant with a foam stabilizing effect to recover the membrane elasticity.
3. Defoamers can promote the drainage of the liquid membrane, thus causing bubbles to collapse
The rate of foam drainage can reflect the stability of the foam. Adding a substance that accelerates foam drainage can also play a defoaming role.
4. Adding hydrophobic solid particles can cause bubbles to collapse
The hydrophobic solid particles on the surface of the bubble will absorb the hydrophobic end of the surfactant, making the hydrophobic particles hydrophilic and entering the water phase, thereby playing a defoaming role.
5. Solubilizing and foaming surfactants can cause bubbles to collapse
Some low-molecular substances that can be fully mixed with the solution can solubilize the foaming surfactant and reduce its effective concentration. Low molecular weight substances with this effect, such as alcohols such as octanol, ethanol, and propanol, can not only reduce the concentration of surfactants on the surface layer, but also dissolve into the surfactant adsorption layer, reducing the tightness between surfactant molecules, thereby weakening the stability of the foam.
6. Electrolytes decompose the double electrical layer of surfactants and cause bubble collapse
For foaming liquids that rely on the interaction of the double electrical layers of surfactants in foam to produce stability, adding ordinary electrolytes can decompose the double electrical layer of surfactants to achieve defoaming effect.
