# US 9,752,238 B2 · Method and formulations for removing rust and scale from steel and for regenerating pickling liquor in hot-dip galvanization process

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- Number: US 9,752,238 B2
- Document ID: US9752238B2
- Status: Granted
- Kind: B2
- Application number: 15/303,051
- Filed: 2015-04-15
- Published: 2017-02-09
- Granted: 2017-09-05
- Earliest claimed: 2014-04-22
- Assignees: Green Future Ltd.
- Applicants: Green Future Ltd.
- Inventors: Reuben Schapiro; Vladimir Boiko; Lev Shapiro
- Web page: https://patentgrep.com/patent/US9752238B2

## CPC

- C23G 1/36: Regeneration of waste pickling liquors
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/024: {by cleaning or etching}
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/08: Tin or alloys based thereon
- C23C 2/36: Elongated material
- C23G 1/083: {solutions containing H3PO4}
- C23G: CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

This invention provides a cost-effective hot-dip galvanization process for ferrous metals, which is regardful to the environment and to the health of the personnel.

## Claims

### Claim 1

A hot-dip galvanization process for stabilizing the surface of ferrous metals comprising steps of
i) removing metal oxide scales and rust from said surface in a pickling stage, comprising contacting said surface with a liquid pickling composition, denoted GF2, comprising phosphoric acid, a hydrophilic polymer, a non-ionic surfactant, and an anti-smut agent, wherein said GF2 solubilizes iron oxides forming said scales and rust without solubilizing non-oxidized metal in said surface, thereby preparing said surface for zinc-coating; and
ii) binding iron from said GF2 solubilized iron oxide in an insoluble iron oxalate complex by contacting said GF2 with a solid composition, denoted GF1, comprising oxalic acid, a nucleation crystallization agent, and an anionic surfactant, and removing said insoluble iron oxalate complex from said liquid composition, thereby releasing phosphoric acid in GF2 for further use;
iii) protecting said surface by coating with a layer of zinc;
the use of GF2 in said step i) preventing the formation of dangerous gaseous side products and resulting in a uniform and thin zinc layer, and the use of GF1 in said step ii) recovering phosphoric acid;
wherein the combination of steps i) and ii) results in an environmentally safe and cost-effective hot-dip galvanization process.

### Claim 2 (depends on 1)

The process of claim 1, wherein said GF2 comprises 7-40 wt % phosphoric acid, 0.5-3 wt % hydrophilic polymer, 0.1-1 wt % non-ionic surfactant, and 0.05-0.5 wt % anti-smut agent.

### Claim 3 (depends on 1)

The process of claim 1, wherein said GF1 comprises 96.5-99 wt % oxalic acid dihydrate, 1-3 wt % of iron oxide as the nucleation agent, and 0.05-0.5 wt % of the anionic surfactant.

### Claim 4 (depends on 1)

The process of claim 1, wherein said hydrophilic polymer comprises polyalkylene glycol, denoted PAG, or polyvinyl alcohol, denoted PVA.

### Claim 5 (depends on 1)

The process of claim 1, wherein said non-ionic surfactant comprises an ether of alkylphenols.

### Claim 6 (depends on 1)

The process of claim 1, wherein said anti-smut agent comprises phosphonic acid, polyphosphonic acid, or an ester thereof.

### Claim 7 (depends on 1)

The process of claim 1, wherein said anionic surfactant is sodium lauryl sulfate, denoted SLS.

### Claim 8 (depends on 1)

The process of claim 1, wherein said nucleation crystallization agent is selected from Fe2O3, Fe3O4, and FeOOH.

### Claim 9 (depends on 1)

The hot-dip galvanization process of claim 1, wherein said step i) comprises preparing a pickle liquor which is essentially composition GF2 or an aqueous dilution thereof, and contacting said surface with said pickle liquor at ambient temperature or at an increased temperature.

### Claim 10 (depends on 1)

The hot-dip galvanization process of claim 1, wherein said step ii) comprises recycling said pickling composition for repeated use.

### Claim 11 (depends on 1)

The hot-dip galvanization process of claim 1, which is a continuous process.

### Claim 12 (depends on 1)

The hot-dip galvanization process of claim 1, wherein said step i) comprises contacting said surface with a pickle liquor consisting essentially of composition GF2 or an aqueous dilution thereof, wherein said hydrophilic polymer is selected from PAG and PVA, said non-ionic surfactant is selected from ethers of alkylphenols, and said anti-smut agent is selected from phosphonic acid, polyphosphonic acid, and esters thereof; and
wherein said step iii) results in creating a thin and uniform zinc layer, thereby reducing the zinc consumption; said hop-dip galvanization process further comprising the steps of
washing and drying said iron oxalate from step ii), thereby obtaining a useful side product of pure iron oxalate.

### Claim 13 (depends on 1)

The hot-dip galvanization process of claim 1, stabilizing the surface of ferrous metals without forming dangerous gaseous side products and without discarding used pickle liquor containing phosphoric acid.

### Claim 14 (depends on 13)

The hot-dip galvanization process of claim 13, comprising
replacing hydrochloric acid or sulfuric acid in the pickling stage by a safer replacement agent which does not form a dangerous gas side-product and which does not excessively dissolve the non-rusty metal surface; and
removing excessive iron from the pickling composition without the evaporation of said composition by employing a precipitating agent,
wherein said replacement agent comprises phosphoric acid and said precipitation agent comprises oxalic acid.

### Claim 15 (depends on 1)

The hot-dip galvanization process for stabilizing the surface of ferrous metals according to claim 1, further comprising the steps of
iv) preparing said composition GF2 containing phosphoric acid, a hydrophilic polymer, a non-ionic surfactant
v) preparing said solid composition GF1 containing oxalic acid, a nuclear crystallizing agent, and an anionic surfactant, and contacting used composition GF2 from step i) with said composition GF1, thereby binding iron in an insoluble iron oxalate complex and recovering said phosphoric acid for further use in said pickling composition; and
vi) washing and drying said iron oxalate complex from step v.

### Claim 16 (depends on 15)

The hot-dip galvanization process of claim 15, wherein said step iv) comprises preparing a concentrate of GF2 composition containing up to 88 wt % phosphoric acid, up to 6 wt % of hydrophilic polymer, up to 1.5 wt % of non-ionic surfactant, and up to 0.8 wt % of anti-smut agent.

### Claim 17 (depends on 15)

The hot-dip galvanization process of claim 15, comprising an increased temperature of 40-95° C.

### Claim 18 (depends on 15)

The hot-dip galvanization process of claim 15, further comprising steps of:
vii) withdrawing at least a portion of the spent pickling composition and transferring it to a regenerating reactor provided with a stirrer and a feeder for feeding GF1 composition;
viii) adding solid GF1 composition into the regenerating reactor, thereby precipitating needle-shaped iron-oxalate; and
ix) withdrawing a slurry comprising the precipitate from the regenerating reactor onto a belt or press filter, and separating iron oxalate from the pickling composition;
x) transferring said pickling composition from step ix) back to the pickling stage;
xi) washing said iron oxalate precipitate with water until pH 4.5-7.0 in the washing liquid and drying the precipitate on the belt filter;
xii) completing water into the pickling composition as a compensation of evaporation; and optionally
xiii) adjusting the concentration of the components in GF2 to a desired level.