{"id":8625,"date":"2025-03-08T16:30:41","date_gmt":"2025-03-08T13:00:41","guid":{"rendered":"https:\/\/yektapajooh.com\/activator-for-use-in-phosphating-processes\/"},"modified":"2025-03-08T16:30:41","modified_gmt":"2025-03-08T13:00:41","slug":"activator-for-use-in-phosphating-processes","status":"publish","type":"post","link":"https:\/\/yektapajooh.com\/en\/activator-for-use-in-phosphating-processes\/","title":{"rendered":"Activator for Use in Phosphating Processes"},"content":{"rendered":"

Activator for Use in Phosphating Processes<\/strong><\/h1>\n

Introduction<\/strong><\/h2>\n

This document concerns a patent filed in Germany. The author intends to explain the application, background, and objectives of the invention and provides specific examples.<\/p>\n

U.S. Patent No. 5,160,551<\/strong>, entitled \u201cActivator for Use in Phosphating Processes,\u201d<\/strong> was filed on April 17, 1991, by R\u00fcdiger Rhein, Dieter Jentsch, and Klaus-Werner Wittel of the Federal Republic of Germany, and assigned to Metallgesellschaft Aktiengesellschaft in Frankfurt.<\/p>\n

Summary of the Patent<\/strong><\/h2>\n

This patent relates to the development of an activating agent based on titanium(IV) phosphate<\/strong> for activating metal surfaces prior to zinc phosphating. The agent contains one or more copper compounds, with a titanium-to-copper weight ratio ranging from 1:100 to 60:1<\/strong>. The composition may also contain additional components such as condensed phosphates, silicates, complexing agents, water-soluble organic polymers, thickeners, and surfactants.<\/p>\n

Application<\/strong><\/h2>\n

The activating agent is used to prepare aqueous activation baths for the treatment of surfaces made of iron, steel, galvanized steel, zinc-alloy-coated steel, aluminum-coated steel, and aluminum<\/strong> prior to zinc phosphating. These baths contain 0.001\u20130.060 g\/L titanium, 0.020\u20131.2 g\/L orthophosphate (calculated as P\u2082O\u2085), and 0.001\u20130.1 g\/L copper<\/strong>. The alkali content is adjusted so that the bath pH is between 7 and 11<\/strong>, preferably between 7.5 and 10<\/strong>.<\/p>\n

The titanium(IV) phosphate-based activating agent designed for activating metal surfaces prior to zinc phosphating contains one or more copper compounds. The Ti:Cu weight ratio is between 1:100 and 60:1<\/strong>. Optionally, the agent may also contain at least one of the following components: condensed phosphate, silicate, complexing agent, water-soluble organic polymer, thickener, and surfactant.<\/p>\n

This agent is used to prepare aqueous activation baths for activating iron, steel, galvanized steel, zinc-alloy-coated steel, aluminum-coated steel, and aluminum prior to zinc phosphating. These baths contain 0.001\u20130.060 g\/L titanium, 0.020\u20131.2 g\/L orthophosphate (calculated as P\u2082O\u2085), and 0.001\u20130.1 g\/L copper<\/strong>. The alkali content is adjusted to maintain a pH between 7 and 11<\/strong>, preferably between 7.5 and 10<\/strong>.<\/p>\n

Title<\/strong><\/h2>\n

Activator for Use in Phosphating Processes<\/strong><\/p>\n

Cross-Reference to Related Application<\/strong><\/h2>\n

This application is related to co-pending application No. 07\/686,800<\/strong>, filed on April 17, 1991. The present invention relates to a titanium(IV) phosphate-based activating agent designed for activating metal surfaces prior to zinc phosphating. The invention also relates to a phosphating method in which this activator is used to prepare activation baths.<\/p>\n

Background of the Invention<\/strong><\/h1>\n

Zinc phosphate layers can be formed on various metal surfaces, such as iron, steel, zinc-alloy-coated steel, aluminum, or aluminum-coated steel, using zinc phosphate-based aqueous solutions. Phosphating solutions may contain, in addition to zinc and phosphoric acid, other cations and anions and are generally applied by spraying, immersion, or a combination of both. The resulting zinc phosphate coatings provide corrosion protection, improved paint adhesion, reduced friction, facilitation of cold-forming operations, and electrical insulation<\/strong>.<\/p>\n

The phosphating process involves several preparation stages. Cleaning the metal surfaces is particularly important and is usually performed using alkaline or acidic cleaners to remove oils, grease, oxides, and solid particles adhering to the metal surface. When mild alkaline cleaners are used, cleaning and surface activation may be combined; however, activation is generally performed as a separate step after cleaning.<\/p>\n

The purpose of activating the metal surface is to ensure the formation of a zinc phosphate layer with fine crystals in the shortest possible time<\/strong>. The effectiveness of an activating agent is determined by the minimum phosphating time required. The ability to form fine-crystalline zinc phosphate coatings can also be evaluated by coating weight or by scanning electron microscope micrographs.<\/p>\n

Titanium(IV) phosphate-based activating agents have produced satisfactory results in practice. Titanium(IV) phosphates are formed by reacting aqueous solutions of titanium(IV) salts with soluble phosphates or phosphoric acid. However, products with activating properties are obtained only under specific production conditions, which are described in detail in U.S. Patents Nos. 2,310,239 and 2,456,947<\/strong>. Even when the reaction conditions remain constant, performance in application technology may vary from one batch to another.<\/p>\n

One disadvantage of using titanium(IV) phosphate-based activating agents is that distilled water must be used<\/strong> to prepare the activation baths, because alkaline-earth metal ions present in tap water can destabilize the activation baths. These ions may also enter the activation bath through used rinse water.<\/p>\n

To prevent the adverse effects of alkaline-earth metal ions and activation-bath instability, DE-A-37 31089<\/strong> proposed adding cation-exchange zeolites with primary particle diameters below 3 micrometers to the titanium phosphate activator. Alternatively, EP-8-180523<\/strong> proposed adding phosphonic acid to the activation bath as a complexing agent, thereby allowing industrial wastewater to be used for preparing the bath. In addition, the presence of phosphonic acid allegedly causes the zinc phosphate coating to have extremely fine crystallites.<\/p>\n

However, the use of phosphonic acids has serious disadvantages. Even at concentrations of only a few milligrams per liter, they can poison phosphating baths and render them unusable within a short period.<\/p>\n

The use of complexing agents in phosphating processes can improve the quality of zinc phosphate coatings and increase the efficiency of activation baths. However, adding these compounds may create environmental concerns because some of them are not readily biodegradable and may accumulate in the environment. Therefore, complexing agents must be selected and used with consideration of their environmental impact and process stability.<\/p>\n

\u201cObjects of the Invention\u201d<\/strong><\/h1>\n

One object of the invention is to provide a titanium(IV) phosphate-based activating agent<\/strong> that can be used to activate metal surfaces prior to zinc phosphating without the disadvantages of known activating agents, that can be produced easily, and that produces stable activation baths with a long service life when used to prepare such baths.<\/p>\n

Another object is to provide an improved activating agent that ensures the formation of fine-crystalline zinc phosphate coatings within a short period of time<\/strong>.<\/p>\n

Another object is to provide an improved phosphating method<\/strong>.<\/p>\n

Description of the Invention<\/strong><\/h1>\n

These and other objects, which will become apparent below, are achieved by an activating agent containing titanium(IV) phosphate and one or more copper compounds<\/strong>, with a titanium-to-copper weight ratio ranging from 1:100 to 60:1<\/strong>. The copper content is adjusted by adding copper compounds, which significantly reduce the phosphating time to a minimum.<\/p>\n

Another result of adding copper is improved stability of the activation bath over a wide temperature range, together with very good activating properties. Almost all copper compounds can be used to introduce copper into the activating agent.<\/p>\n

According to another feature of the invention, the activating agent contains copper compounds introduced in the form of copper hydroxide, copper oxide hydrate, copper tartrate, copper nitrate, and\/or copper phosphate<\/strong>. Although copper sulfate or copper chloride may be used, they are not preferred.<\/p>\n

According to another feature of the invention, an activating agent is provided that additionally contains at least one of the following: condensed phosphates, silicates, complexing agents, water-soluble organic polymers, thickeners, and surfactants<\/strong>. When an activating agent containing such additional additives is used in an activation bath, several additional desirable properties are obtained.<\/p>\n

For example, adding condensed phosphate to the activating agent makes the resulting activation bath less susceptible to hardness-forming elements. A water-soluble organic polymer stabilizes the colloidal titanium(IV) phosphate dispersed in the activation bath and thereby significantly extends the service life of the activation bath. Surfactants reduce surface tension, allowing the titanium phosphate activator to adhere more strongly to the metal surface.<\/p>\n

According to another feature of the invention, the activating agent contains 0.1\u20134 wt.% titanium phosphate<\/strong>, calculated as Ti.<\/p>\n

For the preparation of aqueous activation baths used to activate iron, steel, galvanized steel, zinc-alloy-coated steel, aluminum-coated steel, and aluminum prior to zinc phosphating, the activating agent is used so that the resulting activation bath contains:<\/p>\n