Should we NOT Buffing? What is the Consciousness of Stainless Steel Container Manufacturers?


“Buffing” or “Buff polishing” is often done at the end of stainless steel products. Generally, stainless steel surfaces are shiny because they are buffed.

Buffing removes burrs and scratches during processing and improves surface smoothness. Because it makes a very beautiful appearance, buffing is generally done.

But the beautiful thing is just the appearance. Basically, if you don't buff it, you can keep it clean. In this article, I will explain the reasons for this and NITTO KINZOKU's commitment and consciousness.

1. It is better NOT to do buff-polishing.

1.1 What is Buff-Polishing?

Buff-polishing is a common method of polishing stainless steel surfaces. A disk-shaped “buff” made of cotton or felt is attached to a tool that rotates at high speed, and it is polished by rotating it against the stainless steel surface.

The purpose is mainly to clean the surface and make it shiny and smooth by removing burrs, scratches and dirt from processing. Also, since the surface becomes shiny, it is a polishing that is often done at the final finish from the viewpoint of improving the appearance.

The roughness (fineness) of polishing is often distinguished by a number (like #320, #800, etc.). Generally, the higher the number, the finer the eyes and the more glossy the stainless steel surface. In particular, # 800 buffing is called mirror-finish and produces a mirror-like gloss.

1.2. Disadvantages for buff-polishing

On the other hand, buff polishing has its disadvantages. Although buff polishing makes the surface shiny, but we cannot say it can fulfill the requirements of cleanliness.

When buffing, the polishing powder (a.k a. abrasive) is applied to the buff. Then, the oil of abrasive gets into the invisible small scratches on the stainless steel surface.

Of course, we will clean the tank thoroughly after polishing, but it is difficult to remove this oil completely. In general, these residues will not affect anything, but they are not preferred in pharmaceutical, extraction manufacturers and other fields where sanitary properties are required.

2. Let's take a look at the buffed stainless-steel surface

So what's the difference between buffed stainless steel and non-buffed stainless steel? Because we can't see the surface in details directly by our eyes, so let's use a scanning electron microscope (SEM) to see the photo of the stainless steel surface.

The image above shows a commonly used “2B” stainless steel surface. When buffed, there will be no unevenness like fish scales, but there will be long scratches in a certain direction. You can see that there are many black spots on the image, which are dirt such as abrasive and remain on the surface caused by polishing.

On the other hand, this image may make you feel that “There may be some abrasive left, but isn't it looks beautiful and shiny if we polished the surface by buff?” However, this is a photo of the commonly used “2B material”. So, let's compare this to the “BA material” photo used mainly in our company and see what the difference is.

As you can see, there are more scratches after polishing. There were no deep scratches or noticeable unevenness before polishing, but after buffing, the scratches clearly increased. You can also see dirt (black spots) such as abrasive remains there.

3. Buff polishing by NITTO KINZOKU KOGYO

NITTO KINZOKU KOGYO manufactures products using mainly specially ordered BA materials. The BA material is heat-treated in an oxidation-free atmosphere. This method is called Bright annealing, which produces no oxidation scale on the surface and has a very fine surface roughness. It is a material with a grade higher than 2B material and has a characteristic luster like a mirror.

Example of light reflection of BA material
Example of light reflection of 2B material

As you saw in the previous image, the BA material used in our company is the most beautiful as it is. Buff polishing scratches the surface, and abrasive remains. Such abrasives may cause rouging or corrosion.

Our company is therefore committed to minimizing buff-polishing. Buff polishing is performed only in a limited area to remove machining marks. As you can see in the image below, only about 6.5% of the surface area of containers are buffed (average data for a typical container).

Normal Buff Polishing
Buff-Polishing by NITTO KINZOKU
Polishing-applied Part

From the stage of materials, we selected high-quality materials that do not need polishing and processed without damaging as much as possible. Then, we perform minimum amount of polishing to meet the required quality of the product.
We provide you with the “Only-One” quality. This is the pride of our NITTO KINZOKU KOGYO.

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