**3.1 Cooling water inhibitor**

*Water Chemistry*

Organic amines

**2.7 Picking inhibitor in sulfamic acid**

**3. Inhibitors for near-neutral solution**

growth can also accelerate the local corrosion of metal.

The neutral medium includes circulating cooling water, boiler water, heating water, washing water, oil and gas field injection water and neutral salt water, etc., and the application of corrosion inhibitor is mainly in circulating cooling water system. During the operation of the cooling water in the circulating water system, the concentration of harmful ionic dissolved in the water increases with the continuous evaporation of water, which resulting in deterioration of the quality of the cycle water, and fouling and corrosion of the heat exchanger and the cooling tower. In the open circulating cooling water system, biological slime caused by the microbial

Sulfamic acid is a powdery and moderately acidic mineral acid. In the pickling process, it is stable and good soluble in water. It does not cause salt precipitation and precipitation and does not contain halogen ions. It is suitable for cleaning carbonates and hydroxides. However, it has poor ability to pickle iron oxide, and it decomposes above 60°C. Therefore, it is rarely used for pickling of large boilers and is generally used for pickling of copper pipes. The sulfamic acid pickling inhibitors mainly contain organic amine, dibutylthiourea, dipropynyl sulfide, propargyl alcohol, quaternary ammonium salt, ethyl thiourea, and dodecylamine. The inhibitor of inorganic compound (potassium iodide) also performs excellent performance. **Table 2** is the corrosion inhibition

**(mg/L)**

4000 84.5

N-butyl amine 146 7.1

Twelve amine 380 81.7 Ethylene two amine 120 11.2 Quinoline 258 23.1

Quaternary ammonium salt 1130 91.1

N-cyclohexyl thiourea 313 64.9 1,3-Diethyl thiourea 246 29.5 1,3-Dihexyl thiourea 487 88.0

Dipropargyl sulfide 168 80.5 Acetylene propyl disulfide 220 96.3

Potassium bromide 180 14.6 Potassium iodide 330 79.7

**Corrosion inhibition efficiency (%)**

effects of some organic and inorganic compounds in sulfamic acid.

**Compounds Inhibitor composition Concentration** 

Aliphatic amine fatty acid condensate

Thiourea Thiourea 150 65.1

Alkynes Methyl propargyl alcohol 112 81.2

Inorganic salts Sodium chloride 117 17.3

*The corrosion inhibition effects of some organic and inorganic compounds in sulfamic acid.*

**158**

**Table 2.**

We can select water treatment agents according to the Ryznar index of cooling water or the possible problem. For example, zinc-phosphonate salts as water treatment agents can be chosen for serious erosion in circulating cooling water system, while polyacrylic acid, hydrolyzed polymaleic anhydride, or phosphonate can be used when a large number of scaling has occurred. As the limited compounds in the figure, it cannot be used as a standard method for choosing the right agents. However, it provides the vital reference for the design of the cooling water treatment system.

The complex corrosion inhibitors used in the neutral medium include chromate, phosphate, alkaline zinc/organic, molybdate, silicate, and organic programs. Formulations and chemical programs of some examples are discussed in this section.
