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formation of sludge in zinc phosphating process

Excess Sludge Buildup in Zinc Phosphating Bath

Aug 13, 2010· Phosphating is a conversion coating process in which metal dissolution by the attack of free acid (phosphoric acid) is the basis of coating formation. The ferrous ions formed at the metal/solution interface gets oxidized to ferric ions which in turn combines with the phosphate and gets precipitated as ferric phosphate sludge.

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Phosphate Sludge vanchem

Phosphate sludge is an undesirable waste by-product in an iron and zinc phosphate process. When processing with either iron or zinc phosphate, the chemical reaction produces an insoluble precipitant that is known as phosphate sludge. If ignored, phosphate sludge will accumulate and reduce chemical efficiency and plug-up risers and nozzles in

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Zinc phosphating ScienceDirect

Jan 01, 1999· Contrary to traditional plating operations where electrical current forces the coating formation, zinc phosphating processes rely on the basic pickling reaction that occurs on the metal substrate when the process solution comes in contact with the metal. (sludge) + 2 H+ AI+3 + 6 p-I -+ (AIF6-3) AIF6- 3 + 3NA +-+ Na 3AIF6 (sludge) The

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Removal of zinc from phosphating process sludges

If a phosphating process sludge which contains, e.g., 18.0% P, 15.0% Fe and 0.5% Ca is to be reacted with lime (having a Ca content of 38.5%) at 1100° C., and 0.4 metric t low-grade coke, which contains 3% Si, is to be consumed as fuel and reducing agent per metric t of phosphating process sludge, and if a calcium surplus of 25% is to be

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Formation of zinc–zinc phosphate composite coatings by

iron dissolution and no ferric phosphate sludge formation, which renders it an eco-friendly process. Based on the amount of coating mass as a function of process variables and the potential-time measurement, a pictorial model is proposed for the deposition of zinc phosphate coating. The surface morphology of the coatings exhibits plate-like

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Phosphate Coating an overview ScienceDirect Topics

3.39.2 Zinc Phosphate Coating. Zinc phosphate coating is formed by crystallization on the surface by a chemical reaction. Zinc phosphating should be applied by spray or immersion, and it can be used for any phosphating application. Spray coating on steel surfaces ranges in weight from 1–11 g/m 2, and immersion coating from 1.6–43 g/m 2.

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Zinc Phosphate: Questions and Answers Products Finishing

Jul 01, 2003· Occasionally, a reader may miss a question and answer in one column that may have benefited him/her. Because of this, Products Finishing has developed an article with readers’ questions and answers to zinc phosphating problems. Zinc Phosphate Sludge. Question. We run a zinc phosphate spray coating line where mostly mild steel is treated.

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Formation of zinc phosphate coating by anodic

Sep 07, 2020· The formation of zinc phosphate coating by anodic electrochemical treatment is addressed. The importance of the addition of nitrite, the extent of sludge formation and the eco-friendliness of the

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Modified zinc phosphate coatings: a promising approach to

Zinc phosphate conversion coatings are widely used for increasing corrosion resistance and surface preparation for painting. This kind of treatment has recently been introduced in the field of reinforced concrete. However, the disadvantage in the use of such coatings is the existence of pores. Zinc phosphating baths have constantly been developed and modified by additives in order to enhance

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Modified zinc phosphate coatings: a promising approach to

Jun 07, 2017· Zn2+, leading to thinner zinc phosphate coatings when Ni2+ is present in the coating solution. Second, most Ni2+ deposition occurs during the later stages of the coating process, by nickel phosphate deposition and formation of a Ni-rich corrosion-resistant oxide (Figure 3 & Table 1).

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Zinc phosphating ScienceDirect

Jan 01, 1999· Contrary to traditional plating operations where electrical current forces the coating formation, zinc phosphating processes rely on the basic pickling reaction that occurs on the metal substrate when the process solution comes in contact with the metal. (sludge) + 2 H+ AI+3 + 6 p-I -+ (AIF6-3) AIF6- 3 + 3NA +-+ Na 3AIF6 (sludge) The

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Formation of zinc–zinc phosphate composite coatings by

iron dissolution and no ferric phosphate sludge formation, which renders it an eco-friendly process. Based on the amount of coating mass as a function of process variables and the potential-time measurement, a pictorial model is proposed for the deposition of zinc phosphate coating. The surface morphology of the coatings exhibits plate-like

More

Formation of zinc phosphate coating by anodic

The formation of zinc phosphate coating by anodic electrochemical treatment is addrsed. The importance of the addition of nitrite, the extent of sludge formation and the eco-friendliness of the process is presented. Based on the amount of coating weight and change in potential–time measurements, a mechanism for the coating formation is proposed.

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US20060243600A1 Electrolytic phosphating process

This invention provides a phosphating process that can form a film suitable for a cold forging foundation within 60 seconds and preferably 30 seconds or less. The process uses a treatment bath that is formed of a phosphate ion solution (H 2 PO 4 − +Zn 2+ ), made by dissolving zinc in phosphoric acid, contains phosphoric acid (H 3 PO 4 ), phosphate ions, zinc ions and nitrate ions, may

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Phosphate Sludge Products Finishing

May 22, 2014· What is the composition of phosphate sludge from a zinc-phosphate process bath? What are the precipitates that are formed?—K.P. A. The composition of the sludges generated in a phosphate bath varies with the type of bath in which they are produced. The composition of the sludge found in a zinc-phosphate bath is as follows:

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SURFACE PRETREATMENT BY PHOSPHATE CONVERSION

10. 1937 Spray phosphating Πphospating time: 60-90 seconds 23 11. 1940 Development of non-coating phosphate process based on sodium 24 or ammonium phosphates 12. 1940 Development of cold phosphating methods 25 13. 1941 Phosphating of aluminium surfaces using zinc phosphate

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A safer disposal of hazardous phosphate coating sludge by

Talinli, 2012). Phosphating is the most widely applied system for metal pretreatment process. Surface modification is one the methods to prevent metal from corrosion. During a phosphating process, a metal surface is treated with the aim of giving rise to a hard and electrically non-conducting surface coating of insoluble phosphate (Sankara, 2005).

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Oxsilan thin-film technology: The next generation in metal

zinc-phosphate pretreatment process because it is considered too dirty to be viewed on the tour. Some process tanks contain large quantities of phosphate sludge and the plant is often encrusted with scale deposits. Ongoing and costly chemical or mechanical cleaning

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US7422629B1 Nonsludging zinc phosphating composition and

Electrolysis using a suitable electrolyte provides a completely nonsludging zinc phosphate conversion coating process that produces a high quality conversion coating in a very short time. The suitable electrolyte contains at least water, dissolved nitric acid, and dissolved zinc cations and optionally also contains m chemically distinct species of cations other than zinc and n chemically

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Process description: Conversion coatings (phosphate layer

5.) Sludge formation. Dissolved iron and AlF63- ions from the pickling reaction do not accumulate in the phosphating solution but are precipitated as iron(III) phosphate or triosodium hexafluoroaluminate, respectively. When treating galvanised surfaces and in spraying processes, relatively small amounts of tertiary zinc sludge are formed as well.

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