Steel and iron surface phosphating agent and preparation method thereof

Abstract

The invention provides a steel and iron surface phosphating agent and a preparation method thereof, relating to the technical field of metal surface treating agents. The steel and iron surface phosphating agent comprises the following components in percentage by weight: 3% of potassium dichromate, 3.5% of composite phosphate, 16% of 65% nitric acid, 18% of 85% phosphoric acid, 0.1% of a CyDTA complexing agent, 7% of sodium sulfite and the balance of water. The steel and iron surface phosphating agent can be used for simultaneously phosphating and passivating the surface of a steel pipe; the quantity of acid fog generated by the phosphating agent in the actual production process is relatively low, so that the production environment of a workshop is greatly improved; more importantly, the steel and iron surface phosphating agent can form a uniform and compact phosphating film on the surface of a steel and iron workpiece after being stored for two months, and the problem of effect lowering caused by overlong storage time can be avoided; and in addition, the phosphating agent can also form a compact passivating film on the surface of the steel pipe, and the steel pipe treated by using the phosphating agent has favorable corrosion resistance.

Description

technical field [0001] The invention relates to the technical field of a metal surface treatment agent, in particular to a steel surface phosphating treatment agent and a preparation method thereof. Background technique [0002] Steel parts need to undergo comprehensive surface treatment before painting. The current comprehensive surface treatment process usually includes rust removal, degreasing, phosphating, passivation and other processes. [0003] Phosphating solution is required for phosphating treatment. Currently commonly used phosphating solutions (including the above-mentioned commonly used phosphating solutions) usually have some deficiencies during transportation, storage and use. The specific performance is as follows: the storage time of phosphating solution is mostly It should not exceed one month. After a long storage time, gray sediment will be produced due to oxidation and disproportionation reactions. As a result, the active ingredients in the phosphating s...

AI Technical Summary

Problems solved by technology

[0003] Phosphating solution is required for phosphating treatment. Currently commonly used phosphating solutions (including the above-mentioned commonly used phosphating solutions) usually have some deficiencies during transportation, storage and use. The specific performance is as follows: the storage time of phosphating solution is mostly It should not exceed one month. After a long storage time, gray sediment will be produced due to oxidation and disproportionation reactions. As a result, the active ingredients in the phosphating solution will be damaged, resulting in a decrease in the phosphating effect, and the resulting phosphating film becomes loose

At present, the following methods are usually used for phosphating and passivation treatment of steel pipes in the industry: 1. After phosphating treatment, concentrated acid is used for passivation treatment. This method needs to control the concentration of acid in the treatment tank. If the concentration of acid If it is lower than the critical value, not only will it fail to achieve a passivation effect, but it will also aggravate the corrosion of the steel pipe surface, and this treatment method will generate a large amount of acid mist and the working environment will be harsh

2. Add an appropriate amount of passivation treatment agent to the treatment tank during phosphating treatment, which requires that the ratio of phosphating treatment agent and passivation treatment agent must be within an appropriate range, otherwise it will lead to a reduction in the effectiveness of each other, for example Too much dose of passivation treatment will affect the phosphating effect, resulting in too thin phosphating film