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Pretreatment for plating and coating as an alternative to plasma

Processing details

  • Roughening

Ti coating film formation

Without pretreatmentWithout pretreatment
Film formed after wet blastingFilm formed after wet blasting

What is "thin film coating pretreatment" by wet blasting?

When wet blasting is used as pretreatment for coating, a strong coating film can be formed on the surface by the anchor effect, which provides nano-level fine unevenness having no time dependency.
Wet blasting is a physical process and compatible with a wide range of organic and inorganic materials.

Four features of wet blasting

  • No time dependency   There is no time dependency due to the wettability improved by surface area expansion.
  • No deterioration   Since processing heat is not generated, no deformation or deterioration occurs.
  •  Nano anchor formation   Nano fine uneven surfaces are formed and an anchor effect can be expected.
  • Fast batch processing The etching rate is larger than that of other surface etching methods. The desired etching amount can be obtained in a short time.

Picture of wet blasting

Wet blasting is a technique to project a mixture of abrasive and water at high speed with compressed air against a material to clean, process, and modify its surfaces. This technique allows fine abrasives to be used due to wet processing, and is good at forming a fine uneven surfaces while grinding the surface of the workpiece together with dirt and foreign matter.
In addition, this chemical-free technique is eco-friendly and environmentally friendly, and it is also effective in reducing industrial waste.

For further information, see also "Introduction to wet blasting.” 

ウェットブラスト 処理イメージ

Evaluating the cleaning power of wet blasting

To evaluate the cleaning power of wet blasting, the carbon concentration on the surface was measured.
A comparison of untreated and wet-blasted surfaces shows that the amount of carbon (contamination) on the surface was reduced.

Comparison of element concentrations before and after wet blasting

Comparison of element concentrations before and after wet blasting

Treatment example

Glass x SiO2 coating

Since it is physical processing without chemical etching, such as hydrofluoric acid, the adhesion of the coating is improved without damage like cracks by forming a fine uneven surface that does not make the glass opaque.

Results of cross-cut test

Without pretreatmentPeeling / Without pretreatment
Ra 0.01µm / RzJIS 0.14µm
Film formed after wet blastingWithout peeling / Film formed after wet blasting
Ra 0.05µm / RzJIS 0.37µm
  • Processing condition / abrasive:Polygonal alumina / Air pressure:0.20MPa

Processing example

Abrasive Central particle size(μm) surface
roughness(μm)
Image SEM Bird’s-eye
view
Untreated - Ra=0.023
RzJIS=0.038
未処理写真 未処理SEM 未処理鳥瞰図
Alumina#4000 3.0 Ra=0.025
RzJIS=0.169
アルミナ#4000写真 アルミナ#4000SEM アルミナ#4000鳥瞰図
Alumina#2000 6.7 Ra=0.103
RzJIS=0.574
アルミナ#2000写真 アルミナ#2000SEM アルミナ#2000鳥瞰図
Alumina#800 14 Ra=0.591
RzJIS=1.301
アルミナ#800写真 アルミナ#800SEM アルミナ#800鳥瞰図
Alumina#320 40 Ra=1.071
RzJIS=3.851
アルミナ#320写真 アルミナ#320SEM アルミナ#320鳥瞰図

SUS×TiN coating

Results of scratch test

Untreated workpieceUntreated workpiece
Load: approx. 4.27 N (with peeling)
Wet blasted workpieceWet blasted workpiece
Load: approx. 4.27 N (without peeling)
Results of scratch test

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