What Is Electroplating?
Electroplating is the process of plating a thin layer of other metals or alloys on the surface of certain metals using the principle of electrolysis and is a process of using electrolysis to attach a layer of the metal film to the surface of metal or other materials.
So as to prevent metal oxidation (such as rust), improve wear resistance, electrical conductivity, reflectivity, corrosion resistance (copper sulfate, etc.) and enhance aesthetics.
Metal machinery and parts are surfaces treated by electroplating, which has become the preferred surface treatment method for many parts manufacturers.
When understanding the benefits of electroplating on the parts being machined, two things are often mentioned: protecting the part from wear, and corrosion, and improving the performance of the machined part.
Plating can even increase or decrease the electrical conductivity of a part. Electroless nickel plating and hard chrome plating are the more common surface treatment methods for parts in electroplating technology.
Which one is better and which is better has become a topic of debate among parts machining manufacturers. So this article will help you better understand the difference between hard chrome plating and electroless nickel plating.
What Is Hard Chrome Plating?
If we want to understand the process of hard chrome plating, we need to first understand what hard chrome plating is. Chrome plating is also called industrial chrome. Unlike decorative chrome, its main feature is not the aesthetics of the surface. The role of industrial chromium is to highlight its function and practicality. The main purpose of decorative chrome is to increase the visual appeal of an item by applying a thin layer of chrome. From durability, hard chrome plating is undoubtedly more popular.
Hard chrome plating is the process of applying a chrome layer to the surface of a metal object. The industrial chrome plating process is divided into two steps, that is, degreasing treatment is performed first, and the surface of the parts is cleaned after degreasing. This process is also called substrate treatment.
Of course, under certain conditions, the substrate also needs to be further processed. For example, in order to increase the thickness of the metal surface coating, the operator will place the substrate in an electrochemical cell.
Application of Hard Chrome Plating
Hard chrome plating is defined as industrial chrome that completes the functionalization of the part. There is also a decorative chrome that highlights a strong aesthetic. Although chrome itself is somewhat decorative, it is more suitable for engineering applications than common decorative chrome.
For example, for CNC machine tools in factories, the use of hard chrome technology will prolong the service life of the tool. Since hard chrome plating also has an anti-stick effect, hard chrome coatings are also commonly used on gears and plastic molds. These characteristics also make hard chrome the preferred finish for pistons and shock absorbers of all types of machinery as well as vehicles.
What Is Electroless Nickel Plating?
The electroless nickel plating process mainly uses an inverse nickel-phosphorus alloy to coat and coat the surface of the material. The parts treated by the electroless nickel plating process have strong corrosion resistance, which is beneficial to prolong the service life of the parts.
In fact, about the understanding of electroless nickel plating, we can also compare it with hard chrome plating.
For example, electroless nickel plating will be simpler in process processing, and it does not need to be electrified like industrial chrome plating.
And after cleaning and pretreatment, electroless nickel plating technology will achieve the effect of precipitation coating through a catalytic reaction.
Hypophosphite is often used as a reducing agent in electroless nickel plating. Electroless nickel plating is divided into three grades according to the discharge of phosphorus, namely low phosphorus, medium phosphorus, and high phosphorus.
The phosphorus content of the low-phosphorus coating is about 2% to 5%, while the medium phosphorus content is basically more than 6 %, and the highest can reach 9 %.
High phosphorus is basically more than 10%, and the highest can reach 13%. The most typical is the middle coating, the phosphorus content is basically about 8%. How does the phosphorus content of the coating affect the part? One of the most important is the anti-corrosion performance.
For example, although low phosphorus can make the coating very hard, the anti-corrosion effect is lower than that of medium phosphorus and high phosphorus. Although the hardness of medium phosphorus is not as good as that of low phosphorus, the coating speed is the fastest, which can save a lot of time and labor costs.
Application of Electroless Nickel Plating
Electroless nickel plating is often used in outdoor facilities and parts in the automotive, electronics, petroleum, and other industries because of its easy operation, high hardness, and strong corrosion resistance. Phosphorus coating can be heat treated to increase hardness when electroless nickel plating is used.
Electroless Nickel Plating for Auto Parts: The most common industry for electroless nickel plating is in automobiles, where automakers use electroless nickel plating to protect components such as pistons, fuel injectors, and cylinders.
Similarly, the aerospace industry often uses electroless nickel plating to improve the hardness and corrosion resistance of valves, motor shafts, and other components.
Electroless Nickel Plating for Petroleum, Electronic Products: Electroless nickel plating is not only used in automobiles and aerospace equipment but also plays an indelible and important role in the petroleum and electronic industries.
The use of the electroless nickel plating process can effectively slow down the aging of water pumps and oil pumps and increase their service life.
Nickel plating is also commonly used in electronic products such as hard drives because it improves mold release and anti-sticking capabilities and repairs worn or damaged parts.
Similarities Between Electroless Nickel Plating and Hard Chrome Plating
To distinguish the similarities between hard chrome plating and electroless nickel plating, it is necessary to start with the substrate. Electroless nickel plating and hard chrome plating are both commonly used surface treatment processes, and they are both suitable for unused substrates.
Electroless nickel plating and hard chrome plating are uniformly deposited on the surface of the part to be polished during the plating process, so they are suitable for irregular objects and objects with holes and dents. Both electroless nickel plating and hard chrome plating can cover different materials such as stainless steel, bronze, brass, and plastics.
Electroless nickel plating and hard chrome plating, of which are also very durable and have excellent corrosion resistance. Electroless nickel plating and hard chrome plating, these two surface treatment processes have a low friction coefficient due to their strong sliding properties.
The Difference Between Hard Chrome Plating and Electroless Nickel Plating
- Hard chrome plating is mainly used as a protective decorative coating.
- The performance of the electroless nickel plating layer has the following functions.
The process of electroless nickel plating using sodium hypophosphite as a reducing agent is a Ni-P alloy, and the Ni-P amorphous structure coating can be obtained by controlling the phosphorus content in the coating. The dense coating, low porosity, and corrosion resistance are better than hard chrome plating.
The as-plated hardness of the electroless nickel layer is 450~600HV. After reasonable heat treatment, it can reach 1000-1100HV. In some cases, it can even be used instead of hard chromium.
Electroless nickel plating can control whether the coating is magnetic or non-magnetic depending on the phosphorus content in the coating.
The friction coefficient of the coating is low, and it can achieve a state of oil-free lubrication, and its lubricity and metal wear resistance are also better than those of electroplating.
The low phosphorous coating has good solderability.
- Hard chrome plating is a method of depositing a layer of nickel on the surface of ferrous or non-ferrous metal parts by electrochemical action.
- The principle of electroless nickel plating is that under the catalysis of catalyst Fe, the hypophosphite in the solution catalyzes dehydrogenation on the catalytic surface to form an active hydride, which is oxidized to phosphite; the active hydride is reduced with nickel ions in the solution. The reaction deposits nickel, which itself oxidizes to hydrogen.
- Hard chrome plating can be used as a surface coating but is mainly used for chrome plating as a primer to prevent corrosion, and increase wear resistance, gloss and aesthetics. Widely used in machinery, instruments, meters, medical equipment, household appliances, and other manufacturing industries.
- Due to the comprehensive physical and chemical properties of the electroless nickel plating layer, such as excellent uniformity, hardness, wear resistance, and corrosion resistance, this technology has been widely used, and it is almost difficult to find an industry that does not use electroless nickel plating technology.
According to reports, the proportion of electroless nickel plating in various industries is rough as follows:
Aerospace Industry:9%, automobile: 5%, electronic computer industry: 15%, food industry: 5%, mechanical industry: 15%, nuke industry: 2%, petroleum industry: 10%, plastics industry: 5%, power transmission industry: 3%, printing industry: 3%, pump manufacturing: 5%, valve manufacturing: 17%，others: 6%.
Good durability is the most obvious difference between hard chrome plating and electroless nickel plating. Although both have the effect of prolonging the service life of parts, the hard chrome plating will make the surface hardness of the parts higher, so the hard chrome process will be more durable than electroless nickel plating.
However, electroless nickel plating will make the nickel in the coating durable, and the nickel treated by conventional electrolytic methods will also change color in a short period of time, so the service life of electroless nickel will also be longer, and it is a more economical choice.
Corrosion resistance is the meaning of deep processing of parts, and the purpose of surface treatment is nothing more than two points: beautiful appearance and prolonged service life. Parts treated with hard chrome plating and electroless nickel plating will effectively resist corrosion and increase the service life.
However, research has shown that electroless nickel plating will perform better in natural climates. This is mainly reflected in blind holes. Since blind vias are very difficult to electroplate, electroless nickel plating can be performed in these hard-to-reach places with good results.
Hard chrome plating can be seen from the name that it is its most basic feature. Hard chrome plating can withstand wear, including severe mechanical wear, why is plating so good? Because after electroplating, the Rockwell hardness can reach between 68 and 72.
In contrast, although electroless nickel plating also has good hardness, the hardness of the coating can only reach 63, which is slightly lower than that of hard chrome plating.
Whether it is hard chrome plating or electroless nickel plating, the significance of surface treatment of parts is to improve hardness, corrosion resistance, and aesthetics.
From a manufacturing point of view, hard chrome plating can be used for parts with low requirements for aesthetics, such as large mechanical parts. If there are high requirements for the aesthetics of parts, such as automobiles, lamps, and other fields, electroless nickel plating can be used.
Hard chrome plating, and electroless nickel plating, both of which require polishing on the surface of the part for more uniform coverage. When applying both processes, operators should pay attention to dents, holes, and irregularities in parts.
What to Consider and How to Choose?
Choose hard chrome plating or electroless nickel plating, depending on whether it is a functional requirement or a decorative requirement.
How to choose an electroplating process for a plating type depends on the shape of the part, appearance requirements (some barrel plating is easy to scratch), production cost, environmental protection requirements, the maturity of the selected process, and the difficulty of control.