KR940009677B1 - Baths and process for chemically polishing stainless steel surfaces - Google Patents

Abstract

Baths comprising, in aqueous solution, a mixture of hydrochloric acid, phosphoric acid, nitric acid and sulphosalicylic acid and at least one abietic compound.

Description

Polishing baths and methods for chemical polishing stainless steel surfaces

The present invention relates to a composition of a polishing bath for chemical polishing a stainless steel surface.

The chemical polishing of the metal surface is [electrolytic and chemical polishing of metal] -W. J. Teg. Tegart-Dunod-1960-P. 122 is a well-known technique; This is to treat the metal surface to be polished in an oxidative polishing bath. Polishing baths (US Pat. No. 2,662,814) containing a mixture of hydrochloric acid, phosphoric acid and nitric acid in an aqueous solution are generally used for chemical polishing of austenitic stainless steels. In order to improve the abrasive, suitable additives such as surfactants, viscosity modifiers and brightening agents are usually mixed in these polishing baths. Thus, in US Pat. No. 3,709,824, the composition of a polishing bath for chemical polishing on stainless steel surfaces provides that the aqueous solution contains a phosphoric acid, a mixture of nitric acid and hydrochloric acid, a viscosity modifier selected from a water soluble polymer, a sulfosalicylic acid surfactant and a polishing agent. Doing.

These known polishing baths have the property of corroding metal at a very high rate. Polishing the stainless steel surface by such a polishing bath usually cannot exceed more than a few minutes because of the risk of causing partial corrosion. This high speed action of known polishing baths is disadvantageous in some applications, in particular because they cannot be used to polish the inner wall surfaces of large vessels such as boilers, autoclaves or crystallizers. Since the time required for filling and discharging these containers is usually longer than the optimum duration of chemical polishing, it is virtually impossible to polish the walls evenly, and some parts of the walls are incompletely polished and others are deeply corroded. . Moreover, the high speed action of the known chemical polishing polishing bath makes the control of polishing difficult. In addition, these known polishing baths have a drastic change in some compositions of the polishing bath, so that the recovery of the polishing bath is difficult and cannot be used for contact surface polishing. They are not suitable for polishing large polishing devices, for example heat exchangers with large exchange areas, in comparison with the capacity of the surface to be polished in the polishing bath.

European patent B19.964 (Solvay and Si) proposes a very late acting chemical polishing polishing bath which avoids such drawbacks. These polishing baths consist of a suitable ratio of hydrochloric acid, a mixture of phosphoric acid and nitric acid, sulfosalicylic acid, alkylpyridinol chloride and methyl cellulose.

It can be seen that they are particularly suitable for the homogeneous slow grinding of the surface of austenitic stainless steels of ASTM-340L or ASTM-316L grades of chromium and nickel alloy steels.

Not only can a good polishing be achieved with a different composition of the polishing bath for gentle chemical polishing of austenitic stainless steel surfaces, but also for other grades such as, for example, riveted, welded or bolted assemblies. It is possible to polish steel surface at the same time without the risk of electric corrosion.

Accordingly, the present invention relates to a polishing bath for chemical polishing a stainless steel surface containing hydrochloric acid, a mixture of phosphoric acid and nitric acid and sulfosalicylic acid in an aqueous solution; According to the present invention, the polishing bath contains at least one soluble abietic acid compound in an aqueous solution.

In the polishing bath according to the present invention, the abidic acid compound is an ibethyl group of the following general formula;

Or a compound containing a hydrobiethyl or dihydrobiethyl group.

In accordance with the present invention, the abiotic acid compound should be able to be dissolved in an aqueous solution.

Abiate acid compounds which can be used in the polishing bath according to the present invention include abiateamine.

In particular, abietamine suitable for the polishing bath of the present invention is represented by the following general formula;

Wherein R ₁ represents an abiethyl, hydroabiethyl or dihydroabiethyl group as described above, X ₁ represents a group containing at least one carbonyl group, and X ₂ represents a hydrogen atom or a group containing at least one carbonyl group .)

Examples of suitable aviethamines for the polishing bath according to the present invention are those in which at least one of the groups X ₁ and X ₂ has a group of the following general formula;

-CH ₂ -R ₂

(Wherein R ₂ represents a saturated or unsaturated, substituted or unsubstituted, straight chain or cyclic alkyl moiety containing at least one carbonyl group)

It is preferable that the -CH ₂ -group in these compounds is bonded to the carbonyl group of the R ₂ group via a carbon atom having at least one hydrogen atom. Such substituted abiet amines and the means for obtaining them are described in British Patent -A-734,665.

Examples of abietamines of this type which can be used in the polishing baths according to the invention are the alkyl moieties R ₂ , for example, acetonyl, 2-ketobutyl, 4-methyl-2-keto-3-pentenyl, 4-hydride. Hydroxy-4-methyl-2-ketopentyl, 2-ketocyclopentenyl, 4-hydroxy-2-keto-3-pentenyl, 2-ketocyclopentyl, 4-hydroxy-2-keto-3-phene Tenyl, 2-ketocyclohexyl, 2, 5-diketohexyl and 2-phenyl-2-ketoethyl.

In the chemical polishing bath according to the invention, the respective amounts of hydrochloric acid, phosphoric acid and nitric acid, sulfosalicylic acid and abiate acid compounds are selected according to the nature of the metal to be treated, the working temperature and the desired polishing period.

로 표시되는 술포살리실산의 함량이 염산, 인산과 질산혼합물의 전체 규정농도의 0.05~1.5배인 것이다.A polishing bath according to the present invention suitable for ensuring chemical polishing of chromium and nickel alloy stainless steel surfaces for 2 to 24 hours is characterized in that the aqueous solution contains 1-6 mol of hydrochloric acid, 0.01--1 mol of phosphoric acid, 0.005-0.5 mol of It contains nitric acid, 0.05-20 g of sulfosalicylic acid, and 0.001-3 g of abiotic acid compound. In particular, advantageous polishing baths have a total molar concentration of hydrochloric acid, phosphoric acid and nitric acid mixture of 1-7, preferably 1.8-6, g / g of an aqueous solution.

The content of sulfosalicylic acid is represented by 0.05 ~ 1.5 times the total specified concentration of hydrochloric acid, phosphoric acid and nitric acid mixture.

In a particular form of the polishing bath according to the invention, the polishing bath usually contains alcohols, ethers or ether-alcohols which are dissolved in aqueous solution. The optimum amount of compound added to the aqueous solution of the polishing bath depends on several parameters, in particular the concentration of the additional compound, the selected abiotic acid compound and the polishing bath component. In practice, the concentration of these additional compounds is suitably between 0.001 and 10 g per liter of aqueous solution.

Without changing all other parameters, this type of polishing bath of the present invention results in high quality surface polishing, which is characterized by particularly high gloss.

The polishing bath according to the invention may optionally contain additives, such as surfactants and viscosity modifiers, which are usually present in known polishing baths for chemical polishing of metals.

The polishing bath according to the present invention, bonded to gently polishing austenitic stainless steel surfaces, has the following components per liter of polishing bath solution:

2-5 moles of hydrochloric acid,

0.02-0.5 molar phosphoric acid,

0.01-0.2 mole of nitric acid,

0.1-10 g of sulfosalicylic acid,

0.010-2.5 g of abidic acid compound,

Between 0.002 and 5 g of alcohol, ether or ether-alcohol

0.005-6 g of surfactant.

The great advantage of the polishing bath according to the present invention is that it can be dispensed over several hours after adjusting the respective concentrations of these components, and as a function of speed so that the surface of large dimensions or inaccessible surfaces can be polished uniformly It is the ability to sharpen.

In particular they are more suitable for polishing metal surfaces with very large surface areas compared to the capacity available for polishing baths.

It is also advantageous to use these to polish metal surfaces that are 1 to 10 times the volume (expressed in m 3) of the polishing bath in contact with the metal surface area (denoted in m 2).

The polishing bath according to the invention is suitable for polishing austenitic stainless steel surfaces. In particular, they contain chromium and nickel alloy austenitic stainless steels, especially those containing 12/26% chromium, such as 18/8 and 18/10 / 2.5 steel, 6-30% nickel and 0-6% molybdenum. Better to use to polish.

Moreover, it can be seen that the polishing bath of the present invention can be preferably used to polish other gold steel assemblies, in particular welded assemblies, without causing partial electrical corrosion on the assembly. They are combined with components made of 18/8 grade chromium and nickel alloy steels (ASTM-304 and 304L) and components made of 18/10 / 2.5 grade chromium, nickel and molybdenum alloy steels (ASTM-316 and 316L). Polished welded assemblies.

The invention also relates to a method of polishing a stainless steel surface by bringing the surface into contact with a chemical polishing bath according to the invention.

In the process of the invention, the polishing bath is used at temperatures and pressures that do not cause the risk of its components deteriorating. Therefore, it can be seen that it is advantageous to use a polishing bath at a temperature of 25 ° C. or higher and 100 ° C. or lower, preferably 50 ° to 80 ° under atmospheric pressure.

The contact between the metal surface and the polishing bath is carried out, for example, by dipping in a suitable manner.

In the method according to the invention, the contact time between the surface to be polished and the polishing bath must be sufficient to effectively polish the surface: but it cannot exceed the threshold at which there is a risk of partial corrosion appearing on the surface. The optimum contact time is the metal or alloy constituting the surface to be polished, its shape and initial roughness, the polishing bath composition, the working temperature, the possible turbulence of the polishing bath in contact with the surface, the surface area of the metal surface to be polished, and the volume of the polishing bath to be used. Depends on several parameters such as interrelationships between them; This should be determined in every special case by the usual test method.

In a particular form of the process according to the invention, a metal surface is contacted with a polishing bath, and then a supplemental amount of nitric acid is added to the polishing bath to regenerate it. Supplemental amounts of nitric acid can be added continuously or at intervals. When polishing the metal surface optimally, it can be adjusted to maintain the nitrate concentration in the polishing bath within a range of suitable values.

The advantages of the present invention will be described with reference to Examples.

Example 1

A plate of ASTM-304L stainless steel [chromium (18.0-20.0%) and nickel (8.0-12.0%) alloy steel] plate, surface area 21.50 m 2, was immersed in a 500 cm 3 polishing bath containing the following components per liter at 55 ° C .:

3 moles of hydrochloric acid,

0.15 moles of phosphoric acid,

0.01 mole of nitric acid,

0.5 g of sulfosalicylic acid,

1 g of "Rodine 213" (Amchem Products Inc.) (a mixture of substituted abietamines, isopropanol valent surfactant).

The plate initially has an arithmetic mean roughness Ra _a = 0.27 micron.

After 13 hours of treatment (the polishing bath is constantly stirred), the average depth of corrosion of the metal by the polishing bath is measured at 20 microns. At this time the plate is removed from the polishing bath, washed with water and dried. It has a smooth and glossy appearance. Its glossiness (ASTM standard E430) and its arithmetic mean roughness (R _a ) are measured as follows.

Glossiness: 22%

R _a : 0.13 micron

Example 2

The test described in Example 1 is repeated under the following conditions:

Plates of ASTM-316L grade stainless steel [chromium (16.0 ~ 18.0%), nickel (10.0 ~ 14.0%) and molybdenum (2.0 ~ 3.0) alloy steel.

Surface Area of Plate: 50㎠

Composition of polishing bath (amount equivalent to 1 liter of polishing bath):

2.7 moles of hydrochloric acid,

0.2 mole of phosphoric acid,

0.02 mole of nitric acid,

1 g of sulfosalicylic acid

With 1g "Rodine 213" product

2g "Triton N101" from Rohm and Haas. (Mixture of surfactants based on alkyl aryl polyethers).

Polishing bath temperature: 65 ℃

Polishing Bath Volume: 1,250cm3

Treatment period: 6 hours

Initial roughness of the plate R _a = 0.28 microns

At the end of the treatment the measurements are as follows:

Corrosion Depth: 22 micron

Glossiness: 35%

Roughness R _a = 0.09 microns

Example 3

The test described in Example 1 is repeated under the following conditions:

Plate of ASTM-430 grade martensitic stainless steel [concentration of nickel and carbon 0.75%] and chromium (16.0 ~ 18.0%) alloy steel not exceeding 0.12].

Surface area of plate: 22.50㎠

Composition of polishing bath (amount equivalent to 1 liter of polishing bath):

2.7 moles of hydrochloric acid,

0.2 mole of phosphoric acid,

0.02 mole of nitric acid,

3 g of sulfosalicylic acid

1 g of "Rodine 213" product (as specified in Example 1) and

2 g of "Triton N101" product (specified in Example 2),

Polishing bath temperature: 65 ℃

Polishing Bath Volume: 500cm 3

Treatment period: 10 hours

Initial roughness of the plate R _a = 0.70 microns

At the end of the treatment the measurements are as follows:

Corrosion Depth: 25 micron

Glossiness: 12%

Roughness R _a = 0.22 micron

Example 4

The test described in Example 1 is repeated under the following conditions:

An assembly of two rectangular plates made of stainless steel welded along a common column operation;

Surface area of ASTM-304L grade steel, 30cm2 plate,

Surface area of ASTM-316L grade steel, 30cm2 plate,

Composition of polishing bath (amount equivalent to 1 liter of polishing bath):

4 moles of hydrochloric acid,

0.1 mole of phosphoric acid,

0.02 mole of nitric acid,

1 g of sulfosalicylic acid

1g "Rodine 213" Products

A mixture of 1.3 cm 3 of isopropanol and n-propane.

Polishing bath temperature: 65 ℃

Polishing Bath Volume: 1000cm 3

Treatment period: 10 hours

The plate of the assembly has the following initial roughness:

ASTM-304L Plate: R _a = 0.29 micron

ASTM-315L Plate: R _a = 0.08 micron

When recovered at the end of the treatment, the assembly had a smooth, glossy appearance without any corrosion traces.

Corrosion depth, glossiness and roughness were measured on each plate. :

ASTM-304 plate: Corrosion depth: 27 microns

Glossiness: 21%

Roughness R _a = 0.13 microns

ASTM-316L Plate: Corrosion Depth: 22 micron

Glossiness: 22%

Roughness R _a = 0.11 micron

Claims (10)

A polishing bath for chemically polishing a stainless steel surface containing hydrochloric acid, a mixture of phosphoric acid and nitric acid, and a sulfosalicylic acid in an aqueous solution, wherein the aqueous solution contains at least one soluble abiete acid compound. Polishing bath for grinding. The polishing bath according to claim 1, wherein the Abiet compound is substituted biethyl amine of the following general formula.

Wherein R ₁ represents an abiethyl, hydroabiethyl or dihydroabiethyl group as described above, X ₁ represents a group containing at least one carbonyl group, and X ₂ represents a hydrogen atom or a group containing at least one carbonyl group ) The polishing bath of claim 2, wherein at least one X ₁ and X ₂ group is a group of the general formula: -CH ₂ -R ₂ (Wherein R ₂ represents a saturated or unsaturated, substituted or unsubstituted, straight chain or cyclic alkyl moiety containing at least one carbonyl group) 4. The polishing bath according to claim 3, wherein the -CH ₂ -group in the group of the general formula -CH ₂ -R ₂ is bonded to the carbonyl group of the R ₂ group portion through a carbon atom having at least one minor atom. 5. The alkyl moiety R ₂ according to claim 4, wherein the alkyl moiety R ₂ is acetonyl, 2-ketobutyl, 4-methyl-2-keto-3-pentenyl, 4-hydroxy-4-methyl-2-ketopentyl, 2-ketocyclo Pentenyl, 4-hydroxy-2-keto-3-pentenyl, 2-ketocyclopentyl, 4-hydroxy-2-keto-3-pentenyl, 2-ketocyclohexyl, 2, 5-diketohex A polishing bath, characterized in that selected from yarns and 2-phenyl-2-ketoethyl. The polishing bath according to claim 1, further comprising alcohol, ether or ether-alcohol dissolved in an aqueous solution. The method according to claim 6, for chemical polishing of surfaces of large articles or difficult-to-access surfaces, 2 to 5 moles of hydrochloric acid, 0.02 to 0.5 moles of phosphoric acid, 0.01 to 0.2 moles of nitric acid, and 0.1 to 10 g of sulfosalicylic acid per liter of aqueous solution. A polishing bath, characterized by containing 0.010-2.5 g of abidic acid compound, 0.002-5 g of alcohol, ether or ether-alcohol and 0.005-6 g of surfactant. A method of polishing a stainless steel surface by bringing the surface into contact with a chemical polishing polishing bath, wherein the polishing bath according to any one of claims 1 to 7 is used. The polishing method according to claim 8, wherein the polishing bath is used at a temperature of 40 to 80 캜. 10. The polishing method according to claim 9, wherein the steel surface is brought into contact with the polishing bath, and a supplemental amount of nitric acid is added thereto.