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How to prevent rust of metal products?What is its working principle?
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How to prevent rust of metal products?What is its working principle?

Views: 23     Author: Site Editor     Publish Time: 2019-04-12      Origin: www.fuchun-casting.com

A metal object can be surface coated on the exposed area to achieve high wear, corrosion resistance or thermal insulation. Surface coating can also be used to repair damaged parts. Complete part replacement is then unnecessary and this refurbishment effectively extends the lifetime of the part.


The common denominator for all of these applications is the need to achieve wear, corrosion, heat, abrasion and impact resistance. This combination of properties can be achieved by Electrostatic Spraying Technology.

The characteristics of  are as follows:

(1)The production process has no pollution to the environment and no harm to the human body.

(2) Simple operation and low technical requirements for workers;

(3) Low cost;

(4)The coating has strong adhesion and high corrosion resistance and fall resistance.

Based on this, more and more companies and products choose electrostatic spraying process.

spraying painting

How Does Electrostatic Spraying Work?

The main crux of electrostatic spray painting involves the concepts of charge and electric fields. We are all familiar with these phenomena as most will have witnessed plastic wrap attaching itself to surfaces or clothes sticking to each other as they are removed from a tumble dryer.

With an aerosol, compressed air forces the paint through the end of the spray gun which atomises the liquid into a fine spray. Atomisation essentially breaks up the paint into small droplets and this process is also utilised in electrostatic spraying, but with one unique difference regarding the methodology. The paint is atomised in a static field which is formed at the end of the electrostatic spray gun.


Just before the fog of paint leaves the nozzle, it is given a positive charge. The charged paint droplets are sprayed through a strong electric field which is a term used to describe patterns of forces. The negatively charged, grounded metal item attracts the positively charged liquid to its surface very much like a magnet. Here, a basic law of electricity is inherent in the electrostatic system of spray applying paint, namely that opposite polarities attract. Scientifically, this relatively simple concept is known as Coulomb’s Law which states that the same electrical charges repel each other whereas opposite charges attract as in iron filings to a magnet.


With the continuous development of science and technology, electrostatic spraying is more and more widely used in various aspects, such as decorative spraying of household appliances, instruments, hardware parts, bicycles and so on. It is also used in surface anticorrosive coating of various electric shock, chemical pipelines, valves, etc.



  • What is 'multiple certification'?

    This is where a batch of steel meets more than one specification or grade. It is a way of allowing melting shops to produce stainless steel more efficiently by restricting the number of different types of steel. The chemical composition and mechanical properties of the steel can meet more than one grade within the same standard or across a number of standards. This also allows stockholders to minimise stock levels.

    For example, it is common for 1.4401 and 1.4404 (316 and 316L) to be dual certified - that is the carbon content is less than 0.030%. Steel certified to both European and US standards is also common.

  • What surface finishes are available on stainless steels?

    There are many different types of surface finish on stainless steel. Some of these originate from the mill but many are applied later during processing, for example polished, brushed, blasted, etched and coloured finishes.

    The importance of surface finish in determining the corrosion resistance of the stainless steel surface cannot be overemphasised. A rough surface finish can effectively lower the corrosion resistance to that of a lower grade of stainless steel.

  • Can I use stainless steel at high temperatures?

    Various types of stainless steel are used across the whole temperature range from ambient to 1100 deg C. The choice of grade depends on several factors:

    1. Maximum temperature of operation
    2. Time at temperature, cyclic nature of process
    3. Type of atmosphere, oxidising , reducing, sulphidising, carburising.
    4. Strength requirement

    In the European standards, a distinction is made between stainless steels and heat-resisting steels. However, this distinction is often blurred and it is useful to consider them as one range of steels.

    Increasing amounts of Chromium and silicon impart greater oxidation resistance. Increasing amounts of Nickel impart greater carburisation resistance.

  • Can I use stainless steel at low temperatures?

    Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing.

    Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions.

    Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels show this behaviour at temperatures higher than -100 deg C and in many cases only just below zero.

    In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C.

    Another factor in affecting the choice of steel at low temperature is the ability to resist transformation from austenite to martensite. 

  • Is stainless steel non-magnetic?

    It is commonly stated that “stainless steel is non-magnetic”. This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a relative magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05 – 1.1. 

    It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.

    In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004.

    Martensitic, ferritic, duplex and precipitation hardening steels are magnetic.

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