Ferrous metal water-based rust inhibitor is generally composed of Corrosion Inhibitor, complexing agent, alkali, wetting agent, etc. The substance that plays a key role in the rust prevention process is a corrosion inhibitor. Different inhibitors have different corrosion inhibition mechanisms. Different corrosion inhibitors have different antirust properties. Common inorganic corrosion inhibitors include sodium nitrite, sodium molybdate, sodium tungstate, boric acid, borax, phosphate, etc. They are all anodic oxidation inhibitors. There are more kinds of organic corrosion inhibitors, such as the well-known carboxylic acid salts: mono carboxylic acid, dicarboxylic acid, ternary acid, etc. In addition, fatty acid amides, borate esters, petroleum sulfonates, alkyl succinic acids, cationic quaternary ammonium salts, etc. This kind of corrosion inhibitor contains nitrogen, phosphorus, sulfur, oxygen and other elements with lone pair electrons, which can directly form a chemical adsorption layer on the metal surface. It is a mixed corrosion inhibitor.
Common complexing agents include EDTA, phosphate, etc. The amount and type of complexing agents have a great influence on the rust resistance. The complexing agent chelates with calcium and magnesium ions in water, while the corrosion inhibitor generates sodium salt or potassium salt with free sodium and potassium ions. The univalent sodium salt and potassium salt are foaming themselves, and their adsorption performance is not as good as that of bivalent salt. The reduction of adsorption performance weakens the antirust performance. Only a few complexing agents can enhance the rust resistance. Wetting agent can reduce the surface tension and improve the wettability of rust inhibitor. Most corrosion inhibitors have certain surface activity, so it is generally unnecessary to add additional wetting agent. Instrumental Analysis Method The analysis of ferrous metal rust inhibitor plays an important role in the research and development of rust inhibitor. IR Spectrum Infrared spectroscopy is widely used in the qualitative analysis of small molecules and polymer compounds, which is a relatively simple and fast analysis method. Figure 1 is the infrared matching spectrum of an unknown substance. Through the matching spectrum, we can know that the unknown substance is triethanolamine oleic acid soap, which belongs to mono carboxylate. NMR NMR can be used to analyze and test corrosion inhibitors in rust inhibitors. GC-MS The gas chromatography-mass spectrometer can be used to analyze the volatile solvent in the antirust agent sample. Figure 3 is the GC-MS spectrum of chloroform extract of a water-based corrosion inhibitor, Figure 4 is the mass spectrum of 14.88min outflow substance in the spectrum, and Figure 5 is the matching spectrum of 14.88min outflow substance in the spectrum. Through the matching spectrum, it can be inferred that the water-based antirust agent sample contains triethanolamine borate.
LC-MS
Liquid chromatography-mass spectrometry is used to identify polar compounds in antirust agents, including organic corrosion inhibitors, inorganic corrosion inhibitors, complexing agents, etc. Figure 6 is the MS spectrum of a water-based antirust agent. Through the MS spectrum, it can be seen that there are ternary polycarboxylic acids in the antirust agent.
Liquid phase ion chromatography IC
Liquid phase ion chromatography can analyze inorganic ions in water-based corrosion inhibitor. Figure 7 is the IC spectrum of a water-based corrosion inhibitor. It can be seen from the figure that there is sodium nitrite in the rust inhibitor.
With the requirements of machining and other industries on rust prevention performance and environmental protection getting higher and higher, the rust prevention performance of water-based rust inhibitors will also be improved. The key component is the type and combination of corrosion inhibitors. There are many kinds of corrosion inhibitors. It is difficult to analyze accurately based on a single instrument, but it still requires multiple equipment to conduct joint analysis to obtain an accurate analysis data.
