Treated surface
analysis/control method

Performance/quality control

AMALPHA-treated surfaces can be controlled by several indicators to stabilize the quality.

The functionality of AMALPHA comes from a microscopically roughened metal surface profile, which can be numerically controlled using the amount of etching, L* value, and surface roughness. Numerical control allows the operator to detect signs of degraded treatment conditions and to maintain favorable surface treatment performance.

Measuring the amount of etching by weight-based method

It is possible to determine the amount of etching by measuring the weight of the workpiece before and after etching. Since AMALPHA treatment incorporates etching, it is of critical importance to conduct this measurement to determine whether or not the amount of etching is appropriate.

Measuring the amount of etching by weight-based method

What is the L* value?

The L* value is one dimension used to represent human-recognizable colors in the L*a*b* color space. It approximates lightness as sensed by the human eye and is represented by values between 0 and 100.

Roughened surface profile and L* value

Incident light falling upon a roughened surface with a complex profile is reflected repeatedly in a complex manner. The brightness of the light, or the L* value, decreases in this process of reflection. The L* value can be used to check whether the roughened surface profile is favorable or not since it varies depending on the complexity of the AMALPHA-roughened surface profile and the type of metal.

Light reflected by roughened surface profile

Surface roughness measurement using a laser microscope

Laser microscopes measure surface roughness by casting laser light perpendicularly to a metal surface as a substitute for a probe.
Since AMALPHA-roughened surface profiles look like an indented flask-like structure, laser microscopes are incapable of producing complete measurement results. Consequently, it is difficult to control treated surfaces simply by surface roughness data (Ra, Rz, etc.) obtained using a laser microscope, although such roughness data can be used as a supplementary control indicator. It is recommended to use it as a control indicator along with L* values and the amount of etching.

Surface roughness measurement using a laser microscope

About shelf life

Since AMALPHA forms a microscopically roughened profile on metal surfaces, the treatment continues to be effective unless the profile is impaired. Consequently, a very long period of time is allowable between AMALPHA treatment and the bonding of resin (shelf life). This feature is specifically noticeable with corrosion-resistant metals such as aluminum and SUS.
The results of a molding test using AMALPHA-treated test specimens retained in a room for 11 months showed bonding strength and sealing performance comparable to those of regular test specimens.

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