It has been frequently asked if it is unnecessary to spray paint on the surface of 304/316L stainless steel. Many people commonly believe that since they have chosen 304/316L stainless steel pipes, they should not spray paint it, and doing so is a waste. It is correct; because 304/316L stainless steel tubes already have a good ability to resist corrosion and although generally, it is not necessary to spray paint stainless steel pipes, but nowadays many families choose to paint their surfaces, not only for the basic function of corrosion resistance but also for beautification.
This is because firstly, the surface spray paint is the most effective layer for protection against corrosion. The 304/316L stainless steel tubes themselves are resistant to corrosion, and spraying a layer of paint on their surface preserves them completely.
Secondly, people have a different thought process now; the motive behind choosing stainless steel pipes is to choose a product that is not merely limited to meeting the basic requirements such as rust prevention, but is beautiful also. People now prefer products that are aesthetic and match their own style. This requires the surface treatment of stainless steel pipes.
There are many types of surface treatments for stainless steel pipes such as titanium plating, copper plating, sandblasting and wire drawing, etc., but for the many consumers who are not satisfied with using these methods and require colors of their own choice, spray paint should be used.
Metal surface painting is a method employed to protect the metal from oxidative corrosion. A good spray paint protective layer that is continuous, intact and well combined can act as a barrier to prevent the intrusion of corrosive media. It is used for the special requirements of coating on a material surface and mainly plays the role of decoration and protection against corrosion. This method’s usage objective of protection against corrosion of stainless steel is actually secondary, and mainly it is used to obtain good appearance. Many people ask whether stainless steel surfaces can be painted or not. The answer is yes, they can be spray painted on.
The spray paint is attached to the surface of the stainless-steel tube through the pigment particles of the paint. Consequently, the surface adhesion of the particles with the stainless-steel tube needs to be strong, otherwise the paint would fall off easily later. The surface of stainless steel which is spray painted is usually smooth.
When spraying paint on the surface, a problem is commonly encountered: the paint can be peeled off easily or in other words, it does not stick firmly. if the paint is of good quality, the stainless-steel surface is not treated at all and the paint is sprayed directly. However, If the paint is not suitable for stainless steel, it will still be peeled off even after sanding the surface. In fact, the problem to be solved is not whether the stainless-steel surface can be painted or not – the actual problem is to improve the poor paint adhesion of the stainless-steel surface.
The decorative and protective effect of the coating are not related only to the properties of the metal substrate and the paint itself, but also are directly related to the choice of the metal pre-treatment process. The pre-painting process and quality of the spray paint determine the adhesion of the coating to the substrate, which is closely related to the protective performance of the coating.
There are many types of surface pre-treatment methods for stainless steel metal substrates, which are mainly selected on the basis of the structural characteristics, size and output of the object to be coated. The main purpose of the pre-treatment is to remove any foreign matter from the surface of the substrate while obtaining a suitable surface roughness to facilitate better adhesion of the coating. Traditional surface pre-treatment methods include sanding, sandblasting, pickling and passivation. With the advancement of technology, metal adhesion promoters are now commonly used to solve the problem of poor spray paint adhesion.
The stainless-steel metal adhesion promoter is sprayed between the substrate and the paint coating, and plays the role of connecting and unloading in the form of a hinge such that paint coating can adhere effectively to the substrate. It also improves the adhesion between layers, solves the problem of paint peeling off easily, and can be tested by salt spray. It is not only used for spraying stainless steel surfaces but also widely used in the spraying processes of zinc alloy, aluminum alloy and other materials. In conclusion, its effect of strengthening the adhesion between the surface of metal substrates and the paint coating is obvious while spraying rubber paint on metal hardware or dealing with UV paint, ordinary paint, baking paint or any other problem of paint falling off.
Stainless steel products are very popular and are used a lot in our lives. Especially, stainless steel pipes are widely used in many industries. Many times, for the sake of beauty and better corrosion resistance, the stainless-steel pipe is also painted. The advantages of painting the stainless-steel pipe are that it has a lower cost than copper and thus has a price advantage, and also has a higher corrosion resistance than iron that prevents it from rusting easily. The painting process of the product is not random, and the following steps are to be introduced for painting stainless steel.
- Basic treatment: In order to make the paint film firm in the future, the initial procedure is to clean the surface of the stainless-steel pipe. This treatment method can use a knife to remove any original residual paint, or a sandpaper to sand the surface. After cleaning, sandblasting is used as much as possible to roughen the surface for increasing the adhesion area of the primer;
- Spray primer: The basic role of the primer is to prevent metal surface oxidation and to firmly connect the topcoat and the metal;
- Spray paint: Because of it being in the open air, weather resistance of the paint film is required, and it is difficult to replace the baking paint with a firm paint film. Therefore, it is recommended that polyurethane paint should be used without baking, along with its curing agent at room temperature, a technique which cures very well.
While painting stainless steel pipes, whether by spraying or brushing on it, any kind of paint must be applied for 3-5 times. Also, the paint applied at one time should not be too thick, and a new coat should be applied again only after drying of the previous one. If a person makes a wrong judgement, he will choose to apply it too thick at one time, which is, in fact, wrong. This will give a strong sense of increase in weight, and applying uneven paint will produce flaws.