CN113026027A

CN113026027A - Oil-removing and degreasing powder and preparation method thereof

Info

Publication number: CN113026027A
Application number: CN202110239104.8A
Authority: CN
Inventors: 王初发; 陈衡玲
Original assignee: Guangdong Multi Innovative Materials Technology Co ltd
Current assignee: Guangdong Multi Innovative Materials Technology Co ltd
Priority date: 2021-03-04
Filing date: 2021-03-04
Publication date: 2021-06-25
Anticipated expiration: 2041-03-04
Also published as: CN113026027B

Abstract

The invention relates to the field of metal surface cleaning, in particular to oil removing and degreasing powder for cleaning heavy oil dirt and other dust on the metal surface and a preparation method thereof, wherein the oil removing and degreasing powder comprises the following raw materials in parts by weight: 24-32 parts of an alkaline compound, 40-50 parts of an inorganic salt, 4-6 parts of an auxiliary agent, 11-19 parts of a chelating agent and 6-10 parts of a surfactant; the degreasing powder is suitable for the heavy oil dirt and oil stain penetration effect at normal temperature, can quickly remove various heavy oil dirt and black ash generated by high-carbon steel, has a corrosion inhibition effect on a base material, has good water washing performance, does not contain harmful substances, and is safe and environment-friendly.

Description

Oil-removing and degreasing powder and preparation method thereof

Technical Field

The invention relates to the field of metal surface cleaning, in particular to oil removing and degreasing powder for cleaning heavy oil dirt on the metal surface and other metal dust and a preparation method thereof.

Background

In the metal surface pretreatment, degreasing is a very important step. Oil stains on the surface of metal are brought about from the processing process of materials and various links of part processing, and products such as rust-proof oil and the like are used for rust prevention in the storage and transportation processes.

The prior methods for degreasing and degreasing metal surfaces mainly comprise the following steps: organic solvent methods, chemical methods, electrochemical methods, water-based cleaning agent methods, and the like. The common organic solvent can not completely remove various heavy oil stains, and particularly, other dust such as metal oxides on the heavy oil stains and black ash generated by high-carbon steel can not be effectively cleaned; the chlorine-containing solvent has high toxicity and hydrolysis tendency, and can corrode workpieces under a wet condition; meanwhile, strong acid or strong base is used for chemical and electrochemical wax and degreasing, and metal is corroded, so that the method is not suitable for cleaning; phosphorus-containing cleaning agents cause environmental pollution.

In addition, although the degreasing and degreasing powder on the market at present can clean grease on the metal surface to a certain extent, due to the defects of components, content and process, the degreasing and degreasing powder has poor cleaning effect on heavy grease dirt and black ash generated by high-carbon steel, has poor rust resistance, easily rusts metal parts after cleaning, has more foams in products and poor cleaning efficiency, and needs to be cleaned in a high-temperature environment. In view of the above, an oil and grease removing powder for cleaning heavy oil dirt and other dust on metal surfaces is provided.

Disclosure of Invention

The invention aims to provide oil-removing and degreasing powder for cleaning heavy oil dirt and other dust on the surface of metal at normal temperature and a preparation method thereof, and the invention adopts the following technical scheme for realizing the aim:

the degreasing and degreasing powder comprises the following raw materials in parts by weight: 24-32 parts of alkaline compound, 40-50 parts of inorganic salt, 4-6 parts of auxiliary agent, 11-19 parts of chelating agent and 6-10 parts of surfactant.

Preferably, the alkaline compound is a mixture of potassium hydroxide and sodium hydroxide.

Preferably, the weight ratio of potassium hydroxide to sodium hydroxide is (1.25-1.4): 1.

preferably, the inorganic salt is sodium carbonate.

Preferably, the auxiliary agent is sodium percarbonate.

Preferably, the chelating agent is selected from one or more of citrate, maleic acid acrylic acid copolymerized sodium salt, aminocarboxylic acid, hydroxycarboxylic acid and silicate.

Preferably, the chelating agent is a mixture of citrate and maleic acid acrylic acid co-sodium salt.

Preferably, the citrate salt is sodium citrate.

Preferably, the weight ratio of the sodium citrate to the copolymerized sodium salt of acrylic acid maleate is (1.7-2.7): 1.

preferably, the weight ratio of the chelating agent to the surfactant is (1.5-2.5): (0.8 to 1.2).

Further, the weight ratio of the chelating agent to the surfactant is (1.7-2.5): 1.

preferably, the surfactant is selected from one or more of anionic surfactant, cationic surfactant and nonionic surfactant.

Further, the surfactant is a mixture of a cationic surfactant and a nonionic surfactant.

Further, the nonionic surfactant is coconut monoethanolamide; the cationic surfactant is selected from quaternary ammonium salt or quaternary ammonium base.

Further, the cationic surfactant is a quaternary ammonium salt.

Further, the quaternary ammonium salt is selected from one or more of dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride.

Further, the quaternary ammonium salt is hexadecyl trimethyl ammonium chloride.

Further, the weight ratio of the nonionic surfactant to the cationic surfactant is (1-1.5): (0.8 to 1.2).

The preparation method of the oil-removing and degreasing powder is characterized by comprising the following steps:

s1, adding 24-32 parts of alkaline compound, 40-50 parts of inorganic salt and 4-6 parts of auxiliary agent into a stirrer for dispersing, and mixing and dispersing for 0.5-3 min to form a mixture A; the dispersion rotating speed of the stirrer is 500-800 r/min;

s2, adding 11-19 parts of chelating agent and 6-10 parts of surfactant into a stirrer for dispersing, and mixing and dispersing for 1-5 min to form a mixture B; the dispersion rotating speed of the stirrer is 500-800 r/min;

s3, mixing and stirring the mixture A and the mixture B for 1-3 min to obtain deoiled and degreased powder; the dispersion rotating speed of the stirrer is 500-800 r/min.

Further, the preparation method of the oil-removing degreasing powder comprises the following steps:

s1, adding 14-18 parts of potassium hydroxide, 10-14 parts of sodium hydroxide, 40-50 parts of sodium carbonate and 4-6 parts of sodium percarbonate into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture A; the dispersion rotating speed of the stirrer is 650 r/min;

s2, adding 8-12 parts of sodium citrate, 3-7 parts of maleic acid acrylic acid copolymerized sodium salt, 3-6 parts of coconut monoethanolamide and 3-6 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

s3, mixing and stirring the mixture A and the mixture B for 3min to obtain deoiled and degreased powder; the dispersion rotating speed of the stirrer is 650 r/min.

The invention has the beneficial effects that:

1, the formula components of the degreasing and degreasing powder adopt environment-friendly components, cleaning liquid formed in the using process of the degreasing and degreasing powder does not pollute the environment, the washing property is good, harmful substances are not contained, and the requirements of European Union ROHS are met.

2, the degreasing powder can effectively and thoroughly remove heavy oil dirt on the surface of the metal base material, black ash and other dust generated by high-carbon steel, has no watermark and does not have residue on the surface of the metal base material.

3, the compound surfactant is adopted as a raw material, has strong emulsification, permeation and stripping effects on heavy oil dirt on the surface of the metal substrate at normal temperature, and can efficiently clean the metal surface.

4, after cleaning, a protective film is formed on the surface of the metal base material, so that the surface of the metal base material is prevented from being oxidized, and the difficulty of cleaning and maintaining in the later period can be reduced.

Detailed Description

In one embodiment, the alkaline compound is a mixture of potassium hydroxide and sodium hydroxide.

In one embodiment, the weight ratio of potassium hydroxide to sodium hydroxide is (1.25-1.4): 1.

in one embodiment, the inorganic salt is sodium carbonate.

In one embodiment, the adjuvant is sodium percarbonate.

In one embodiment, the chelating agent is selected from one or more of citrate, maleic acid acrylic acid copolymer sodium salt, aminocarboxylic acid, hydroxycarboxylic acid, silicate.

Chelating agent: reacting a metal atom or ion with a ligand containing two or more coordinating atoms to form a complex having a cyclic structure, which is called a chelate; such ligand substances capable of forming chelates are called chelating agents, also known as complexing agents.

In a preferred embodiment, the chelating agent is a mixture of citrate and copolymerized sodium acrylate maleate.

Citrate salt: the salt is a salt with strong capability of chelating calcium ions at low temperature, but the chelating capability is reduced when the temperature is increased.

In a preferred embodiment, the sodium citrate is available from Shaanxi Chengming Biotech, Inc. under CAS number 68-04-2.

In a preferred embodiment, the copolymerized sodium salt of maleic acid and acrylic acid is available from Shanghai Bizhao Biotech, Inc. under CAS number 26677-99-6.

In a preferred embodiment, the weight ratio of the sodium citrate to the copolymerized sodium salt of acrylic acid maleic acid is (1.7-2.7): 1.

in a preferred embodiment, the weight ratio of the chelating agent to the surfactant is (1.5-2.5): (0.8 to 1.2).

In a more preferred embodiment, the weight ratio of the chelating agent to the surfactant is (1.7-2.5): 1.

in a preferred embodiment, the surfactant is selected from one or more of an anionic surfactant, a cationic surfactant, and a nonionic surfactant.

Anionic surfactant: anionic surfactants are classified according to the structure of their hydrophilic groups: sulfonates and sulfate salts are currently the major class of anionic surfactants. The various functions of surfactants are mainly manifested in changing the properties of the surface, liquid-liquid interface and liquid-solid interface of a liquid, of which the surface (interfacial) properties of the liquid are most important.

Cationic surfactant: the cationic surfactant is mainly a nitrogenous organic amine derivative, and because the nitrogen atom in the molecule of the cationic surfactant contains lone pair electrons, the cationic surfactant can be combined with hydrogen in acid molecules by hydrogen bonds to enable amino groups to carry positive charges; therefore, they have good surface activity in acidic media; and is easy to precipitate in an alkaline medium to lose surface activity; besides the nitrogen-containing cationic surfactant, a small part of cationic surfactant containing elements such as sulfur, phosphorus, arsenic and the like is also available.

Nonionic surfactant: the nonionic surfactant is a surfactant which contains an ether group which is not dissociated in an aqueous solution as a main hydrophilic group in a molecule, and the surface activity of the surfactant is represented by neutral molecules; the nonionic surfactant has high surface activity, good solubilization, washing, antistatic, calcium soap dispersion and other performances, small irritation, and excellent wetting and washing functions. The pH value range of the surfactant can be wider than that of a common ionic surfactant, and the surfactant can also be used together with other ionic surfactants, and the surfactant of the system can be improved by adding a small amount of nonionic surfactant into the ionic surfactant; nonionic surfactants can be classified into polyoxyethylene type, polyhydric alcohol type, alkanolamide type, polyether type, amine oxide type, and the like according to the structure of the hydrophilic group.

In a preferred embodiment, the surfactant is a mixture of a cationic surfactant and a nonionic surfactant.

In a preferred embodiment, the nonionic surfactant is coconut monoethanolamide.

In a preferred embodiment, the cationic surfactant is selected from quaternary ammonium salts or quaternary ammonium bases.

In a preferred embodiment, the cationic surfactant is a quaternary ammonium salt.

Quaternary ammonium salts: is a compound formed by replacing four hydrogen atoms in ammonium ions with hydrocarbyl, and has a general formula R₄NX, wherein the four hydrocarbon radicals R may be identical or different.

In a more preferred embodiment, the quaternary ammonium salt is selected from one or more of dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride.

In a more preferred embodiment, the quaternary ammonium salt is cetyltrimethylammonium chloride.

In a most preferred embodiment, the cetyltrimethylammonium chloride is available from Shanghai Seiki chemical Co., Ltd under CAS number 112-02-7.

In a more preferred embodiment, the cocoyl monoethanolamide is purchased from the wash stocks plant dada, tokyo city, CAS No. 68140-00-1.

In the experimental process, the sodium citrate and the sodium acrylate copolymer maleate are added in a matching way, and can be matched with Ca in the solution in the cleaning solution²⁺、Mg²⁺、Fe²⁺Plasma complexing to form a stable complex; reduction of Ca²⁺、Mg²⁺、Fe²⁺The interaction of the metal ions and the hydrophilic groups of the surfactant improves the washing effect, and the sodium citrate and the ions on the surface of the metal base form a strong combination effect, so that the black ash of high carbon steel generated on the surface of the metal base material and the metal ions of other metal impurities can be complexed to form soluble particles, and the ash deposition resistance and the cleaning and dirt redeposition performance can be improved; when the addition amount of the maleic acid acrylic acid copolymerized sodium salt is small, the cleaning dirt cannot be effectively dispersed in the cleaning liquid, and the cleaning efficiency is reduced; when the amount of sodium citrate added is small, the number of the interaction networks with cetyltrimethylammonium chloride and coconut monoethanolamide decreasesNo effective protective film can be formed on the surface of the metal substrate, and Ca²⁺、Mg²⁺、Fe²⁺The plasma can be complexed in the surfactant, so that the emulsifying capacity of the surfactant to oil stains is reduced, the surface of the metal base material cannot be effectively cleaned, the corrosion inhibition effect on the surface of the metal base material cannot be realized, and the cleaning solution can corrode the surface of the metal base material; when the amount of the surfactant is increased, the greasy dirt on the surface of the metal substrate can be effectively treated, but the amount of cleaning foam is increased in the cleaning process, so that the surfactant is wasted.

Preferably, the weight ratio of the nonionic surfactant to the cationic surfactant is (1-1.5): (0.8 to 1.2).

Further, the weight ratio of the nonionic surfactant to the cationic surfactant is (1-1.5): 1.

in the experimental process, the fact that not all nonionic/cationic surfactants are matched for use is unexpectedly found, heavy oil dirt on the surface of a metal base material can be efficiently cleaned at normal temperature, the nonionic surfactants are coconut monoethanolamide, the cationic surfactants are hexadecyltrimethylammonium chlorides, and the use ratio is (1-1.5): 1, under the action of hydrogen bonds, the bonding force between molecular chain segments is enhanced, a network structure is formed, the stability of the network structure between surfactants is improved, the heavy oil dirt can be comprehensively covered, infiltration and emulsification are carried out, the density of cleaning foam is improved, the heavy oil dirt can be efficiently removed, and the cleaning dirt can be prevented from being deposited.

A preparation method of deoiling and degreasing powder comprises the following steps:

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any inventive step based on the embodiments of the present invention, belong to the scope of protection of the present invention, and the present invention is described below by way of specific embodiments, but is not limited to the specific embodiments given below.

Example 1

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate, 5 parts of sodium percarbonate, 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride.

The maleic acid acrylic acid copolymerized sodium salt is purchased from Shanghai Beizhu biological science and technology limited, and has a CAS number of 26677-99-6.

The sodium citrate is purchased from Shaanxi Chengming Biotech Co., Ltd, and has a CAS number of 68-04-2.

The hexadecyltrimethylammonium chloride was purchased from Shanghai Xuejie chemical Co., Ltd, CAS number 112-02-7.

The coconut monoethanolamide was purchased from a wash raw material plant of dada, tokyo, having a CAS number of 68140-00-1.

s1, adding 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate and 5 parts of sodium percarbonate into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture A; the dispersion rotating speed of the stirrer is 650 r/min;

s2, adding 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 2

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 18 parts of potassium hydroxide, 14 parts of sodium hydroxide, 50 parts of sodium carbonate, 6 parts of sodium percarbonate, 12 parts of sodium citrate, 7 parts of maleic acid acrylic acid copolymer sodium salt, 6 parts of coconut monoethanolamide and 4 parts of hexadecyl trimethyl ammonium chloride.

s1, adding 18 parts of potassium hydroxide, 14 parts of sodium hydroxide, 50 parts of sodium carbonate and 6 parts of sodium percarbonate into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture A; the dispersion rotating speed of the stirrer is 650 r/min;

s2, adding 12 parts of sodium citrate, 7 parts of acrylic acid copolymerized sodium maleate, 6 parts of coconut monoethanolamide and 4 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 3

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 14 parts of potassium hydroxide, 10 parts of sodium hydroxide, 40 parts of sodium carbonate, 4 parts of sodium percarbonate, 8 parts of sodium citrate, 3 parts of maleic acid acrylic acid copolymer sodium salt, 3 parts of coconut monoethanolamide and 3 parts of hexadecyl trimethyl ammonium chloride.

s1, adding 14 parts of potassium hydroxide, 10 parts of sodium hydroxide, 40 parts of sodium carbonate and 4 parts of sodium percarbonate into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture A; the dispersion rotating speed of the stirrer is 650 r/min;

s2, adding 8 parts of sodium citrate, 3 parts of acrylic acid copolymerized sodium maleate, 3 parts of coconut monoethanolamide and 3 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 4

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate, 5 parts of sodium percarbonate, 10 parts of sodium citrate, 3 parts of maleic acid acrylic acid copolymer sodium salt, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride.

s2, adding 10 parts of sodium citrate, 3 parts of acrylic acid copolymerized sodium maleate, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 5

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate, 5 parts of sodium percarbonate, 5 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride.

s2, adding 5 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 4.8 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 6

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate, 5 parts of sodium percarbonate, 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 10 parts of coconut monoethanolamide and 4 parts of hexadecyl trimethyl ammonium chloride.

s2, adding 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 10 parts of coconut monoethanolamide and 4 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Example 7

The degreasing and degreasing powder comprises the following raw materials in parts by weight: 15 parts of potassium hydroxide, 12 parts of sodium hydroxide, 45 parts of sodium carbonate, 5 parts of sodium percarbonate, 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 1.6 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride.

s2, adding 10 parts of sodium citrate, 5 parts of acrylic acid copolymerized sodium maleate, 1.6 parts of coconut monoethanolamide and 3.2 parts of hexadecyl trimethyl ammonium chloride into a stirrer for dispersing, and mixing and dispersing for 2min to form a mixture B; the dispersion rotating speed of the stirrer is 650 r/min;

Test of

Testing the cleaning effect of the degreasing powder prepared in the embodiments 1-7 on degreasing of stainless steel workpieces;

the surface of a stainless steel workpiece with the thickness of 10cm multiplied by 10cm is treated, and the method comprises the following steps:

(1) mixing 10 parts by weight of crude oil, 10 parts by weight of heavy diesel oil and 10 parts by weight of refined oil residue to obtain a mixed solution A, and adding the mixed solution A into a stainless steel container to heat the mixed solution A to 80 ℃;

(2) drying 7 cleaned stainless steel workpieces, immersing the stainless steel workpieces into the mixed solution A, storing for 3h, extracting, standing and drying;

(3) placing the gold stainless steel workpiece with the surface immersed in the mixed liquid A in an oven, and drying for 30min at 100 ℃;

(4) weighing 35g of the degreasing powder prepared in the embodiment 1-7, adding the weighed degreasing powder into ultrasonic equipment, and then adding 1L of water;

(5) and (3) respectively putting 7 stainless steel workpieces with surfaces soaked with oil into ultrasonic equipment for cleaning.

The following test results were obtained after washing and are shown in table 1:

TABLE 1

The description and applications of the present invention are illustrative, and not intended to limit the scope of the invention to the embodiments described above, therefore, the present invention is not limited by the embodiments, and any technical solutions obtained by equivalent substitution are within the scope of the present invention.

Claims

1. The oil-removing degreasing powder is characterized by comprising the following raw materials in parts by weight: 24-32 parts of alkaline compound, 40-50 parts of inorganic salt, 4-6 parts of auxiliary agent, 11-19 parts of chelating agent and 6-10 parts of surfactant.

2. The degreasing powder of claim 1, wherein the chelating agent is selected from one or more of citrate, maleic acid acrylic acid copolymer sodium salt, aminocarboxylic acid, hydroxycarboxylic acid, and silicate.

3. The degreasing powder of claim 2, wherein the chelating agent is a mixture of citrate and a copolymerized sodium salt of maleic acrylic acid.

4. The oil and fat removing powder as claimed in claim 1, wherein the weight ratio of the chelating agent to the surfactant is (1.5-2.5): (0.8 to 1.2).

5. The oil and fat removing powder as claimed in claim 4, wherein the weight ratio of the chelating agent to the surfactant is (1.7-2.5): 1.

6. the degreasing powder of claim 1, wherein the surfactant is selected from one or more of anionic surfactant, cationic surfactant, and nonionic surfactant.

7. The degreasing powder of claim 6, wherein the surfactant is a mixture of a cationic surfactant and a nonionic surfactant.

8. The degreasing powder of claim 7, wherein the non-ionic surfactant is coconut monoethanolamide; the cationic surfactant is selected from quaternary ammonium salt or quaternary ammonium base.

9. The oil and fat removing powder as claimed in claim 7, wherein the weight ratio of the nonionic surfactant to the cationic surfactant is (1-1.5): (0.8 to 1.2).

10. The preparation method of the oil-removing degreasing powder as set forth in any one of claims 1 to 9, comprising the steps of: