Polyurethane waterproof coating catalysts – amine catalysts

2021-12-03   Pageview:108

Amine catalysts are generally used in the production of polyurethane foam and are divided into the following categories.
Aliphatic amine catalysts include N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N’,N’-tetramethylene-alkylenediamine, triethylamine, N,N-dimethylbenzylamine, etc.
The alicyclic amine catalysts include solid amine, N-ethyl morpholine, N-methyl morpholine, N,N’-diethylpiperazine, etc.
The catalysts of alcohol compounds are triethanolamine, DMEA, etc.
Aromatic amines include pyridine, N,N’-dimethylpyridine, etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Type of corrosion inhibitor
Paint corrosion inhibitors (corrosion inhibitors) are generally divided into oxidation type, precipitation film type, metal cation type and organic compound type.

(1) Oxidation types such as chromate, nitrite, molybdate and tungstate, etc., wax water emulsion which are themselves oxidants or use dissolved oxygen in the medium as oxidants, which can form dense yF egO on the metal surface; protective film, The thickness of this protective film is between 5 and 10 nm, which hinders the metal ionization process, thereby slowing down the corrosion of the metal.

For chromate and nitrite, regardless of whether there is oxygen in the medium, they can inhibit metal corrosion, but due to their toxicity, they are eliminated in many paints. As for molybdate and tungstate, since they are not oxidizing, there must be oxygen in the medium to have corrosion inhibition. Oxidizing corrosion inhibitors have high corrosion inhibition efficiency and good performance. It has been widely used, but if the amount is insufficient, large cathodes and small anodes may be formed on the metal surface and pitting corrosion may occur. Therefore, they are also called “dangerous corrosion inhibitors”. However, molybdate and tungstate are still very important as oxidizing corrosion inhibitors. As early as the 1970s, the Xuanwei company in the United States used calcium chromate for water-based paints and zinc chromate for solvent-based paints.

(2) Precipitation film type. They can react with the relevant ions in the medium and form a corrosion-inhibiting precipitation film on the cathode area on the metal surface. The ions of the non-oxidizing inhibitor do not directly participate in the formation of the oxide film. Their function is To solve the discontinuity of the oxide film, the micropores in the defective part of the coating film are blocked by the deposition of anions. In most cases, the precipitation film is formed in the cathode area and covers the surface of the cathode, separating the metal from the corrosive medium, and inhibiting the electrochemical corrosion of the metal. Sometimes it can also cover the entire surface of the metal while inhibiting the electrochemical corrosion of the metal. Anode process and cathode process. Therefore, this type of corrosion inhibitor can be divided into two types: cathodic inhibition type and mixed inhibition type.

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