Technical assistance: Pre-film formation issue in circulating water systems
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This post was last edited by hesonchang214 on 2010-4-21 at 17:18. How long does the effect of pre-coating circulating water last? Under what circumstances is it necessary to re-coat with film?
The duration of the effect after pre-coating is directly related to various factors such as the quality of the coating itself, the operating conditions of the circulating water, the quality of the circulating water, and system management. If done properly, this duration can reach several decades; otherwise, pre-coating will need to be repeated after just a few months of operation. Whether pre-coating is necessary depends on the degree of corrosion in the system.
If it dries after pre-coating, it can remain intact for a long time. It’s similar to phosphating in steel mills. Apply a new coating after corrosion occurs.
This post was last edited by cdpulin on 2010-6-7 15:15; it depends on the operating conditions. In addition to the degree of corrosion, two other points need attention: First, the chemical cleaning of the system must be thorough, ensuring that the surface of the carbon steel is completely clean; to prevent the redeposition of suspended particles in water, the turbidity of the water must remain below 20 mg/l throughout the process. Secondly, the pH value must be carefully controlled. If the pH is too low, a protective film cannot be formed; even if a film does form, it may dissolve. If the pH is too high, precipitates such as calcium phosphate form in the water and deposit on the metal surface, affecting the quality of the film formed.