A kind of seawater circulating cooling water phosphorus-free environment-friendly carbon steel composite corrosion inhibitor and its preparation and use method

Abstract

The invention discloses a phosphorus-free environment-friendly carbon steel composite corrosion inhibitor using seawater circulating cooling water as well as preparation and use methods of the carbon steel composite corrosion inhibitor. The composite corrosion inhibitor is prepared by molybdate or tungstate, gluconate, rare-earth salts, zinc salts and a stabilizing agent. Based on the characteristic of difficulty in passivation of carbon steel in the seawater, the characteristic of the seawater circulating cooling process and the system economic operation requirement, a compound multi-element pretreatment filming agent with high concentration is firstly adopted, and then, a process for multi-element compound treatment of corrosion inhibitor with low concentration during normal operation is adopted, so that the purposes that the corrosion inhibitor with high concentration is quickly film-formed and the corrosion inhibitor with low concentration keeps running and repairing films are fulfilled; and moreover, the corrosion velocity of the carbon steel is controlled to be less than 0.02mm / a, and the corrosion inhibition rate is controlled to be more than 98 percent. The corrosion inhibitor product has wide sources of raw materials, is good in solubility and high in cost performance, does not pollute ocean environment, and belongs to low-poisonous grade industrial products; and moreover, the corrosion inhibitor is compatible to seawater scale inhibition and dispersion agents and bacteria-algae inhibitors.

Description

technical field [0001] The invention relates to the technical field of industrial circulating cooling water treatment, and more specifically relates to a phosphorus-free and environment-friendly carbon steel composite corrosion inhibitor for seawater circulating cooling water and a preparation and use method thereof. Background technique [0002] As an environmentally friendly water-saving technology, seawater circulating cooling has huge potential application demands in high water-consuming industries such as electric power, chemical industry, petrochemical, and steel. The development and utilization of seawater instead of fresh water as industrial circulating cooling water is an important way to alleviate my country's coastal cities and regions. One of the important ways to protect the marine ecological environment due to the shortage of fresh water resources. [0003] In the seawater circulating cooling system, the corrosion of metal materials by seawater is the primary pr...

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Problems solved by technology

[0004] However, there are still some problems to be solved in terms of technology, economy, and environmental protection: (1) The experimental conditions cannot well simulate the operating conditions of the seawater circulating cooling system (temperature, flow rate, concentration ratio, etc.), and the research results are in the seawater cooling system. (2) The technical indicators of corrosion inhibition need to be improved, and the corrosion inhibition effect of some composite corrosion inhibitors developed is acceptable, and the corrosion rate of carbon steel is basically controlled within the 0.075mm specified in the design specification for seawater circulating cooling water treatment. Near the boundary of / a, there is not much space for corrosion inhibition allowance; (3) The cost of water treatment is high, and the single agent or compound formula of corrosion inhibitor is used in large amounts in seawater, such as the unit price of sodium molybdate or sodium tungstate is extremely high, and Use higher concentration

Moreover, it is preliminarily estimated that the cost per ton of water treatment of some composite corrosion inhibitors is several times or even dozens of times higher than the average level of existing industrial cooling water. The cost of use is very expensive, and it is not practical and market competitive in seawater cooling systems; (4) ) discharge water will be restricted by environmental protection. For a long time, phosphorus (phosphine) corrosion inhibitors, which are easy to cause eutrophication of water bodies, have occupied the mainstream of water treatment agents. In recent years, restricted by national and local sewage discharge standards and marine environmental protection, In the field of cooling water treatment, the voice of "limiting phosphorus" and "banning phosphorus" has once again been raised. Some phosphorus-containing and refractory water treatment agents are gradually losing their competitive advantages in the market and are facing the situation of being eliminated. Phosphate-free water treatment technology has been Become the focus of the industry