Stainless steel surface treatment process

 Stainless steel has unique strength and superior anti-corrosion properties. At the same time, it has high wear resistance and is not easy to rust. Therefore, it is widely used in the chemical industry, food machinery, electromechanical industry, and household appliance industry. The application and development prospects of stainless steel will become wider and wider, but the application and development of stainless steel largely determine the degree of development of its surface treatment technology.

Introduction of stainless steel varieties

Stainless steel generally contains high-quality metal elements such as chromium (CR), nickel (NI), molybdenum (MO), and titanium (TI). Common stainless steels include chromium stainless steel and nickel-chromium stainless steel. Classification from the metallographic structure of stainless steel: austenitic stainless steel, martensitic stainless steel

Stainless steel surface treatment varieties

• Whitening treatment of the natural color of the surface
• Surface mirror stone bright treatment
• Surface coloring treatment

1. The surface natural color whitening treatment

In the process of processing, the stainless steel undergoes coiling, edge binding, welding, or the handler’s warm surface fire treatment, resulting in a black oxide scale. This kind of hard gray-black oxide scale was usually removed by a strong corrosion method with hydrofluoric acid and nitric acid in the past. However, this method is costly, pollutes the environment, and is harmful to the human body. The corrosion is relatively large, and it is gradually eliminated.

At present, there are two kinds of treatment methods for this kind of oxide scale: (1) Using shot peening/sandblasting method. (2) Use chemical methods.

2. Mirror bright treatment method of stainless steel surface

According to the complexity of stainless steel products and the different requirements of users, mechanical polishing, chemical polishing, electrochemical polishing, and other methods can be used to achieve mirror stone luster.

Mechanical polishing

Good leveling performance, bright labor intensity, serious pollution, difficult to process complex parts, reduced gloss, high investment, and cost. Simple workpieces, medium and small products, and complex parts cannot be processed. The gloss of the entire product is not consistent, and the gloss retention time is not long.

Chemical polishing

Low investment, complex parts can be polished, high efficiency, high speed, insufficient brightness, polishing liquid to be humidified, gas overflows, and wind-friendly equipment is required.

Electrochemical polishing

Mirror gloss, long-term maintenance, stable process, less pollution, low cost, and good anti-pollution performance. The one-time investment is large, and the complicated parts must be equipped with tooling and auxiliary electrodes.

3. Surface coloring treatment

Stainless steel coloring not only imparts various colors to stainless steel products, increases the variety of products, but also improves the wear resistance of products.

There are several coloring methods for stainless steel:

(1) Ion deposition of oxides or oxides

(2) High-temperature oxidation method

(3) Chemical oxidation method, electrochemical oxidation method

(4) Gas-phase cracking method

Briefly describe the overview of various methods:

(1) The ion deposition oxide or oxide method is to place the stainless steel workpiece in a vacuum coating machine for vacuum evaporation plating; this method is suitable for mass product processing. Because of the large investment and high cost, small-batch products are not economical.

(2) The high-temperature oxidation method is to immerse the workpiece in a specific molten salt to maintain a certain process range, so that the workpiece forms a certain thickness of oxide film, and presents a variety of different colors.

(3) The chemical method is to form the color of the film through chemical oxidation in a specific solution. However, if the color of a batch of products is consistent, it must be controlled by a reference telegram.

(4) The electrochemical method is to form the color of the film through electrochemical oxidation in a specific solution.

(5) The gas-phase cracking method is more complicated and less used in industry.

Electroplating surface treatment methods

Electroplating is a method in which metal is precipitated from the electrolyte by the action of an applied current and deposited on the surface of the object to obtain a metal covering layer.

Galvanized:

Zinc is easily corroded in acids, alkalis, and sulfides. The zinc layer is generally passivated. After passivation in chromate solution, the passivation film formed is not easy to interact with moist air, and the anti-corrosion ability is greatly enhanced. In dry air, zinc is relatively stable and not easy to change color. In water and humid atmosphere, it reacts with oxygen or carbon dioxide to form an oxide or alkaline carbonic acid film, which can prevent zinc from continuing to oxidize and play a protective role.

Applicable materials: steel, iron parts

chrome:

Chromium is very stable in a humid atmosphere, alkali, nitric acid, sulfide, carbonate solutions, and organic acids, and is easily soluble in hydrochloric acid and hot concentrated sulfuric acid. The disadvantage is that it is hard, brittle, and easy to fall off. Direct chromium plating on the surface of steel parts as an anti-corrosion layer is not ideal. Generally, multi-layer electroplating (ie copper plating → nickel → chromium) can achieve the purpose of rust prevention and decoration. At present, it is widely used to improve the wear resistance of parts, repair size, light reflection, and decoration.

Applicable materials: ferrous metal, copper, and copper alloy zero decorative chrome plating, wear-resistant chrome plating

Copper plating:

Copper is not stable in the air, and at the same time, it has a high positive potential and cannot protect other metals from corrosion. However, copper has high electrical conductivity, the copper plating layer is tight and fine, it is firmly combined with the basic metal, and it has good polishing performance. It is generally used to improve the conductivity of other materials, as the bottom layer of another electroplating, as a protective layer to prevent carburization, and to reduce friction or decoration on the bearing.

Applicable materials: black metal, copper, and copper alloy nickel-plated, the chrome-plated bottom layer

Nickel plating:

Nickel has good chemical stability in the atmosphere and lye and is not easy to change color, but it is easily soluble in dilute nitric acid. It is easy to passivate in concentrated nitric acid, and its disadvantage is porosity. To overcome this disadvantage, multi-layer metal plating can be used, and nickel is the intermediate layer. The nickel plating layer has high hardness, is easy to polish, has high light reflectivity and can increase the appearance and resistance, and has good corrosion resistance.

Applicable materials: can be deposited on the surface of various materials, such as steel-nickel-based alloys, zinc-based alloys, aluminum alloys, glass, ceramics, plastics, semiconductors, and other materials

Tin plating:

Tin has high chemical stability. It is not easy to dissolve in dilute solutions of sulfuric acid, nitric acid, and hydrochloric acid. Sulfides have no effect on the tin. Tin is also stable in organic acids, and its compounds are non-toxic. It is widely used in food industry containers and parts of aviation, navigation, and radio equipment. It can be used to prevent copper wires from being affected by sulfur in rubber and as a protective layer for non-nitriding surfaces.

Applicable materials: iron, copper, aluminum, and their respective alloys

Copper tin alloy:

Copper-tin alloy electroplating is to plate copper-tin alloy on the parts without nickel plating, but directly chromium plating. Nickel is a relatively rare and precious metal. At present, copper-tin alloy electroplating is widely used in the electroplating industry to replace nickel plating, which has good anti-corrosion ability.

Applicable materials: steel parts, copper, and copper alloy parts

Complete guide about Waterproof Hardwood flooring

Today's flooring market provides us with a lot of options. Solid hardwood flooring is a great choice if you want to add value and aesthetics to your property. But before taking any step, it is vital to collect basic information that will help in the process. Hardwood flooring has been widely used in residential and commercial buildings, but waterproofing is always a difficult problem to solve. So, is there a kind of floor that not only has good waterproof performance but also can take into account the natural and aesthetic feelings that traditional hardwood floors bring us? Then, we should get to know the waterproof hardwood floor, let us have a deeper understanding and more details.

What is waterproof hardwood flooring?

If we look at the outer look, then waterproof hardwood flooring looks precisely the same as solid hardwood floorings. But the extra features and qualities create the real difference. In simple words, the added layer is the main reason that makes the difference. The companies use some specific techniques and technologies to give a high-quality look. Apart from this, the added layer adds durability. But the method of producing varies according to the manufacturer. Generally, most manufacturers use these steps to create waterproof flooring.

• Step 01: Take a composite material made up of stones or ultra-hard polymers.
• Step 02: Use a layer of real wood on top of composite material
• Step 03: Attach waterproof sealants and pads for an extra soft feel under the feet

However, these steps could be different and depend on the manufacturer. If you take services from a professional, you can’t tell the difference between such an engineered floor and a traditional floor. Moreover, the following areas are preferred to use waterproof flooring options.

Bathrooms	Kitchen	Entry spaces
Mudrooms	Basement

So, if you don’t want to replace your floor more often, go with the engineered waterproof flooring. After installing, you only require basic cleaning and polishing to keep the place in perfect condition.

What are the reasons to use waterproof hardwood flooring？

There are plenty of reasons due to which you should go behind the waterproof flooring options.

• The waterproof flooring options can work excellently in wet locations.
• Apart from this, the waterproof floor will not swell if it gets wet.
• Above all, the waterproof floors are easy to clean. For instance, you can remove the debris by using a swifter mop, micro mop, broom, or vacuum.
• It is worth mentioning that a waterproof floor doesn’t change colors or swell like solid wood. So, due to this feature, it is becoming the best choice for commercial and residential use.

Pros & cons of waterproof flooring options:

Despite the above reasons, plenty of other pros will instigate you to give the waterproof hardwood flooring a chance. So, here is the list that will make the decision easier.

Pros	Cons
It helps to reduce the cost that incurs to repair water damages	It doesn’t work fine if water is there for more than 48 hours
Best to maintain the aesthetics of the space
You don’t need to replace it again & again.
Easy to install.

What are the different available waterproof flooring options?

Earlier, we have discussed everything about engineered waterproof flooring and know the basic concept. But before using this option, do your homework to learn about available opportunities. Generally, floorings are made up of two types of material:

The above illustration is showing that inorganic material like synthetic plastic is better than Organic one. Organic material refers to material like solid/traditional hardwood, or bamboo and all of these are plant-based. Thus, the organic material often quickly gets exposed to the water. But all the organic materials are not harmful, and different manufacturers are using these to make waterproof flooring. Here is the list of all those materials that could use in the flooring.

Good flooring options	Acceptable options	Poor choices
Porcelain tile	Engineered hardwood flooring	Solid hardwood
Ceramic tile	Laminate flooring	Solid hardwood (pre-finished)
Sheet Vinyl	Linoleum sheets	Carpeting
Luxurious Vinyl flooring	Bamboo hardwood flooring
Vinyl Tile

The names in “Good list” make a great choice, but engineered hardwood flooring makes a great choice if you want to add aesthetics. Apart from this, it’s vital to mention that laminate floors are cheaper to install and buy.

Are you ready to clean up the water mess? Seek professional advice:

Engineered hardwood flooring indeed makes the floor appealing and stylish. But it’s not as simple as it is looking. Yes, seeking professional advice and choosing a good quality waterproof hardwood flooring are two crucial things. So, in this regard, “EONSTAR” is a trustworthy and most reputable waterproof hardwood floor dealer in the market. The quality of the company’s products is unmatchable with these features:

Brand name	EONSTAR
Primary motto	Meet the needs of a multidimensional lifestyle with quality
Main serving markets	USA, Germany, Japan, Malaysia, and Turkey
Deals in	SPC flooring, fireproof wood floor, PVC, and wood veneer SPC floor
Highlighted qualities	Reliable service with Customization

You can contact the company anytime to place the order, even with Customization. EONSTAR uses 100% authentic products and one of the leaders in producing waterproof hardwood flooring. So, even if you want to place an order in bulk, get in touch with them. Before making a decision, prepare a list of available brands, their products, and prices. But always go with the one that offers quality and is reputable in the market.

The difference between pickling, phosphating, and passivation

In an effort to prevent corrosion or simply improve appearance, engineers will often specify an additional finishing treatment process for a portion, or all, of a metal part’s exterior surface after it has been machined or fabricated.

No matter what the reason, each of these metal surface treatment finishing processes plays an important role in the manufacturing process:

Pickling

The definition of pickling

Acid is used to remove oxide scale chemically according to a certain concentration, temperature, and speed, which is called pickling.

Pickling classification

• According to the type of acid: sulfuric acid pickling, hydrochloric acid pickling, nitric acid pickling, hydrofluoric acid pickling. Pickling must choose different media according to the material of the steel, such as pickling carbon steel with sulfuric acid and hydrochloric acid, and pickling stainless steel with mixed acid of nitric acid and hydrofluoric acid.
• According to the shape of steel: wire pickling, forging pickling, steel plate pickling, strip steel pickling, etc.
• According to the type of pickling equipment: tank pickling, semi-continuous pickling, full continuous pickling, tower pickling.

The principle of pickling

Pickling is the process of chemically removing the oxide scale on the metal surface, so it is also called chemical pickling. The iron oxide scale formed on the surface of the steel pipe is an alkaline oxide that is insoluble in water. When they are immersed in an acid solution or sprayed on the surface of the acid solution, these alkaline oxides can undergo a series of chemical changes with the acid.

Because the iron oxide scale on the surface of carbon structural steel or low-alloy steel is loose, porous and cracked, and the iron oxide scale undergoes repeated straightening, stretching, and conveying along with the strip steel on the pickling line, these pores and cracks further increase and expand, so while the acid solution chemically reacts with the iron oxide scale, it also reacts with the base iron of the steel through the cracks and pores. That is to say, at the beginning of pickling, three kinds of chemical reactions between iron oxide scale and metallic iron and acid solution are carried out at the same time.

1. The iron oxide scale reacts chemically with acid and is dissolved (dissolution).
2. Metal iron reacts with an acid to generate hydrogen, which mechanically peels off the iron oxide scale (mechanical peeling action).
3. The generated atomic hydrogen reduces iron oxides to ferrous oxides that are easy to react with acid, and then react with acid to be removed (reduction).

Passivation

The Principle of passivation

The passivation mechanism can be explained by film theory. That is to say, passivation is due to the action of metal and oxidizing substances, which produces a thin and dense passivation film on the metal surface with good covering performance, and can also be firmly adsorbed on the metal surface. Passivation film firmly adsorbed on the metal surface. This film exists as a separate phase, usually a compound of oxidized metal. It plays the role of completely separating the metal from the corrosive medium, preventing the metal from contacting the corrosive medium, so that the metal basically stops dissolving and forming a passive state to achieve the role of anti-corrosion.

Advantages of passivation

1. Compared with the traditional physical sealing method, the passivation process has the characteristics of absolutely no increase in the thickness of the workpiece and no change in color, which improves the precision and added value of the product, and makes the operation more convenient; 　　
2. Since the passivation process is carried out in a non-reactive state, the passivation agent can be added and used repeatedly, so the life is longer and the cost is more economical.　　
3. Passivation promotes the formation of the oxygen molecular structure passivation film on the metal surface, the film layer is dense, the performance is stable, and it has a self-repairing effect in the air at the same time, so compared with the traditional method of applying anti-rust oil, the passivation formed The passivation film is more stable and corrosion-resistant.　　

Most of the charge effects in the oxide layer are directly or indirectly related to the thermal oxidation process. In the temperature range of 800-1250℃, the thermal oxidation process with dry oxygen, wet oxygen, or water vapor has three continuous stages. First, the oxygen in the ambient atmosphere enters the formed oxide layer, and then the oxygen diffuses into the inside through the silicon dioxide. When it reaches the Si02-Si interface, it reacts with silicon to form new silicon dioxide. In this way, the oxygen entry-diffusion-reaction process continues to occur, so that the silicon near the interface is continuously converted into silicon dioxide, and the oxide layer grows into the silicon wafer at a certain rate.

Phosphating

Phosphating treatment is a kind of chemical reaction to form a layer of film (phosphating film) on the surface of a surface treatment process.

The phosphating process is mainly used on the metal surface. The purpose is to provide a protective film for the metal surface to isolate the metal from the air and prevent it from being corroded. It is also used for the primer before the painting of some products. With this layer of phosphorus, The chemical film can improve the adhesion and anti-corrosion ability of the paint layer, improve the decoration and make the metal surface look more beautiful, and can also play a lubricating role in the cold working of some metals.

After phosphating treatment, the workpiece will not be oxidized and rusted for a long time. Therefore, the application of phosphating treatment is very wide, and it is also a commonly used metal surface treatment process, which is more and more used in automobiles, ships, machinery manufacturing, and other industries.

Classification and application of phosphating

Normally, a kind of surface treatment will show one color, but phosphating treatment can show different colors by using different phosphating agents according to actual needs. This is why we often see phosphating The processing is gray, colored, or black.

Iron-based phosphating: After phosphating, the surface will appear iridescent and blue, so it is also called color phosphor. The phosphating solution is mainly made of molybdate, which will form an iridescent phosphate film on the surface of steel materials. It is also mainly used for coating the bottom layer to achieve the anti-corrosion ability of the workpiece and improve the bonding force of the surface coating.

Phosphating wastewater treatment process

 Phosphating wastewater is the pretreatment of metal surface treatment, generally including degreasing and rust removal, surface conditioning, and phosphating passivation.

Phosphating wastewater treatment process description:

1. Chemical removal of zinc

Chemical methods for removing zinc include the sulfide method and alkali method coagulation precipitation.

2. Phosphorus removal by chemical precipitation by the lime method

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Adding lime milk clarified liquid and adjusting the pH value to 10~11, most of the phosphate in the wastewater can be precipitated and removed. The lime milk also neutralizes while removing phosphorus.

3. Phosphorus removal and oil removal by coagulation air flotation

The addition of flocculant makes the residual phosphorus in the wastewater and other pollutants undergo a coagulation reaction, and the flocs produced are attached to the air floatation method to produce a large number of fine bubbles, and the bubble buoyancy is used to bring them out of the water. At the same time as dephosphorization, it can also absorb and remove oil droplets. The bubble rises fast, and the operation is safe and reliable. It is an economical and practical deoiling technology.

4. Activated carbon adsorption phosphorus removal

Activated carbon is the most commonly used adsorbent in water treatment. It has good adsorption performance and chemical stability is not easy to break and has low airflow resistance. The commonly used ones are powder and granular. The process utilizes the huge specific surface area of activated carbon to fully adsorb trace residual phosphorus and other pollutants in wastewater.

5. Stirring and mixing device

Both the primary and secondary reactors are equipped with stirring devices. The stirring speed in the tank is gradually reduced by using a pulley or a reducer to meet the needs of stirring and mixing at different stages in the entire reaction process, making the reaction more thorough and more conducive to the subsequent precipitation Process. The pipeline mixer in the process makes the neutralization reaction easier when adding H2SO4, and can make the effluent pH value fully meet the standard.

6. Discharge mud by gravity or water pressure

The sludge or scum produced in the primary and secondary reactors and air flotation tanks in the system are regularly discharged into the sludge thickening tank by gravity or hydraulic pressure to be concentrated and then transported to landfill after natural drying. The clear liquid is returned to the conditioning tank for physical and chemical treatment.

7. Backwashing and desorption

Both the silica sand filter and the activated carbon adsorber in the system need to be backwashed regularly to prevent clogging, and the wastewater produced by them is returned to the regulating tank. In addition, in order to regenerate the activated carbon, a high-temperature heating regeneration method is used to activate, and water vapor is used to desorb the granular carbon in the activated carbon filter to ensure the normal adsorption effect.

Top 5 Things to Consider When Choosing Commercial Flooring

Finding the right commercial flooring manufacturer for a commercial location can be challenging. You can research each type of flooring option at Eonstar floor; when planning a commercial renovation, keep trustworthy commercial flooring suppliers in mind.

Choosing the best floor covering for a commercial flooring installation needs careful thinking. This piece will go over 5 factors you should consider when choosing highly functional yet beautiful floor coverings.

What are the 5 considerations for commercial flooring?

Floor covering is an essential component of commercial building interiors. In addition to withstanding heavy activity in the workplace, office flooring serves as a cozy element. It may also be utilized to make a statement or define your style, as office environments have grown less rigid and formal.

In the modern age of dynamic corporate culture, it is insufficient to examine utility alone when selecting a suitable choice for commercial flooring. Here are five points to consider if you are trying to establish a modern workplace or change an existing office into a trendier workplace.

1. Long-term viability

Although it is not a new phenomenon, more and more people are becoming environmentally concerned, and external conditions are becoming pre-requisite considerations in many design projects. Sustainable, reusable, and recycled materials are taking over the floor covering market, as they are more eco-friendly than traditional materials.

While certain materials have better reputations than others. At Eonstar, a large range of options are available, allowing for a wonderful blend of textures, appearance, and feel.

2. Unique Designs

The traditional workplace was frequently drab, stiff, and overly formal in its appearance and operations.

Due to the increasingly diverse and youthful workforce, offices incorporate more innovative designs to attract and retain young workers.

Therefore, geometric designs (such as hexxtiles and herringbone) and vibrant colors (Visualize and Trend) rapidly replace classic monochrome commercial flooring. This element has played a significant role in the rise of modular flooring in the business sector, attributed to its versatility and ability to blend in with any workspace design.

3. Luxurious flooring

A luxurious luxury floor is no longer reserved for the wealthy and well-off but is becoming increasingly popular in commercial settings.

Designers are incorporating luxury vinyl tiles produced from high-quality, low-cost materials and attractive, textured carpet tiles into office designs to provide elegance and comfort. This is a part of the residential trend, and it provides significant real benefits to an organization.

4. Safety

Safety has a significant impact on the workplace, and it should be a primary consideration in the design of workspaces. To protect the workplace safety of your employees, you must check that the flooring material you choose complies with commercial flooring standards.

Consideration of slip resistance when selecting flooring for a workstation is an important element, especially the floor coverings in entrances and locations where spills may be more common than usual.  

Consideration of barrier tiles and entry matting systems has significant safety implications, as well as the added benefit of making the remainder of your floor covering more visually appealing and easier to keep updated.

5. Maintenance 

Commercial floors may wear out faster than household floor coverings due to excessive usage. They can also become filthy faster than residential building floors. Before installing any business flooring material, you must consider its longevity and ease of maintenance.

This is easily rectified by examining the manufacturer’s cleaning and maintenance instructions and the various flooring symbols contained on the standard documentation of a commercial flooring manufacturer.

The wear rating class, the castor chair test, and features such as stain resistance and colorfastness are among the most important.

What type of flooring is good for commercial use?  

When choosing a commercial flooring material for your business, consider that maintenance costs may exceed the initial material and installation prices.

Here are five long-lasting materials that demand less maintenance:

1. Quarry Tile

Quarry tile is a tough flooring option, and it has limited design options. Quarry tile also requires minimal upkeep. Daily maintenance should consist of cleaning and mopping with a cleaner after each shift. 

2. Carpet Tile

Carpet tile is a long-lasting and easiest-to-maintain soft-surface flooring option. When a broadloom carpet is damaged, a complete roll of carpet must be replaced. When a carpet tile becomes stained, simply replace it. Carpet tile requires less labor, material, and time to maintain than broadloom carpet.

3. Wood Flooring

It is possible to find solid wood flooring in a wide variety of selections. Hardwood flooring is a traditional choice in parts because of its long-lasting quality (when properly cared for) and the fact that it never goes out of style.

It adds a sense of effortless sophistication and warmth to any environment, no matter how large or small.

4. Epoxy Floors

A thermosetting resin is placed on a concrete substrate to increase durability and aesthetic appeal. These systems are easy to install and maintain. If properly applied, the coatings will be chemical and abrasion-resistant for years. 

Epoxy flooring requires daily sweeping, deep cleaning every few months, and spot cleaning as needed. Epoxy systems are low-maintenance for commercial and industrial applications.

5. Polished concrete

Polished concrete is easy to install and maintain in industrial settings. To install polished concrete, we first harden the concrete with a chemical densifier. Then we polish with a grinder and seal with a sealant that comes in different colors.

Polished concrete is resistant to chemical spills, oil stains, and even forklift traffic. Like epoxy floors, polished concrete simply requires sweeping and spot cleaning, with occasional deep cleaning. While initially more expensive than laminate or VCT, its low maintenance needs reduce overall costs.

These solutions, while not exhaustive, will give long-term value through durability and ease of maintenance. 

Final thought

Choosing the best flooring material starts with selecting the best commercial flooring supplier. Eonstar has quite a lot of experience in many different flooring projects,   we are able to offer clients the solution on which materials offer the best value  in terms of initial cost, the convenience of installation, and long-term maintenance expenses, and we are ready to serve you

Hydrochloric acid pickling process control

In the Hydrochloric acid pickling process control, the most important thing is to control the pickling time and life of the pickling tank to ensure the maximum productivity and service life of the pickling tank.

To obtain the best pickling effect, first, control the concentration of hydrochloric acid, and secondly control the content of iron ions (iron salts) in the pickling solution. Because not only the concentration of acid will affect the pickling effect of the workpiece, the content of iron ions (iron salt) will reduce the mass fraction of the pickling solution, which will also affect the pickling effect and speed of the workpiece. It is worth noting that to obtain the best pickling efficiency, the pickling solution must also contain a certain amount of iron ions (iron salts).

Control of the hydrochloric acid washing tank

(1) Pickling time

The pickling time basically depends on the concentration of hydrochloric acid/iron ion (iron salt) and the temperature of the pickling solution.

(2) Best pickling

The best pickling effect of the workpiece should be when the concentration of hydrochloric acid and the concentration of precipitated iron ions (iron salts) reach a relative balance.

(3) Remedy for decreased acid effect

When the pickling solution decreases or loses its pickling effect due to the saturation of iron ions (iron salt), it can be diluted with water to restore the pickling function. Although the concentration of hydrochloric acid is reduced, it can still perform the pickling function, but at a slower rate. If new acid is added to the pickling solution with saturated iron content, the concentration of the new hydrochloric acid solution will fall above the saturation point, and the pickling of the workpiece will still be impossible.

(4) Treatment measures after acid solubility drops

After the pickling solution has been used for a period of time, its concentration decreases and even becomes waste acid. However, the manufacturer cannot recover the acid at this time and still retains a certain use-value. To use the reduced concentration of low acid, at this time, the workpiece that needs to be re-dipped due to partial leakage in the hot-dip galvanizing is generally put into Among them, pickling and reprocessing is also an effective use of waste acid.

Method of replacing old acid with hydrochloric acid pickling solution:

When the iron salt in the old acid exceeds the specified content, it should be replaced with a new acid. The method is that the new acid accounts for 50% and the old acid is added to the new acid after precipitation. The amount of the old acid is ~50%. A part of the old acid is used to maintain an appropriate amount of iron salt in the pickling solution because the hydrochloric acid Iron salts with a content of less than 16% can increase the activity of the pickling solution.

However, with the advancement of hot-dip galvanizing technology, the amount of old acid added must be carried out based on strictly controlling the iron salt content of the old acid, and the iron salt concentration of the newly prepared hydrochloric acid solution must be controlled within the range.

Workpiece steel material and pickling speed

The pickling speed varies with the composition of the steel workpiece to be pickled and the scale produced.

The carbon content in steel has a great influence on the dissolution rate of the steel matrix. When the carbon content increases, the dissolution rate of the steel matrix increases rapidly.

The dissolution rate of the steel workpiece matrix after cold and hot processing will increase, and the dissolution rate of the steel matrix after annealing the steel workpiece will decrease. In the iron oxide scale on the surface of steel workpieces, the dissolution rate of iron monoxide is higher than that of ferroferric oxide and ferric oxide. The rolled iron sheet has more iron monoxide content than the annealed iron sheet. Therefore, its pickling speed is also faster. The thicker the iron oxide layer, the longer the pickling time. If the thickness of the scale is uneven, it is easy to produce local defects of “under-pickling” or “over-pickling”. If you want to know more, please contact us.