As is known to all, sodium tungstate as a new type of corrosion inhibitor is non-toxic，harmless and environmental friendly. To achieve better corrosion effect, the adding amount of sodium tungstate needs to be higher. In order to reduce the amount of sodium tungstate and better inhibit pitting corrosion at the same time, sodium tungstate should mix with other corrosion inhibitors to achieve synergies.

 

Sodium lauroyl sarcosine (SLS) is a new type of corrosion inhibitor developing in recent years. It’s white to pale yellow liquid and has a special odor. It’s soluble in water, ethanol, glycerol alcohol and aqueous solution. In normal conditions, it’s relatively stable to heat, acid and alkali. It has low toxicity, low irritation and is easily biodegradable. Cost is reasonable. In metal processing it is often used as a corrosion inhibitor, rust remover and so on.

 

Mentioned in the previous article, using weight loss method and electrochemical method can determine corrosion inhibition of sodium tungstate and SLS composite to carbon steel in simulated seawater. Through the experiment we can draw the following conclusions:

1. In the simulated seawater, sodium tungstate has the corrosion inhibition effect on carbon steel. Corrosion inhibition efficiency increases with the increase of its concentration. Sodium tungstate adsorption is the mixed adsorption on the surface of the carbon steel.

2. After adding SLS, the corrosion effect increases greatly. After adding 40 mg/L SLS and 600 mg/L sodium tungstate, corrosion inhibition efficiency increases from 62% to 84.4%. It shows both have synergy effect. Comparing corrosion lacing film situation, pitting corrosion decreases significantly after adding SLS. When the SLS adding amount is 60 mg/L, pitting corrosion phenomenon disappears.

3. One-component sodium tungstate inhibitor requires high concentration. After adding the composite corrosion inhibitor, polarization resistance becomes larger which shows that composite corrosion inhibition effect is more obvious. It has a synergistic effect. When the 600 mg/L sodium tungstate and 120 mg/L SLS compositing, corrosion inhibition efficiency is more than 95% and corrosion rate also drops below 0.075 mm/a. it belongs to mixed type inhibitor. 

In a word, sodium tungstate and sodium lauroyl sarcosine composite is better than single use and has good synergistic corrosion inhibition effect. The composite corrosion inhibitor is mixed type corrosion inhibitor.