Surface analysis of 316 stainless steel treated with cold atmospheric plasma

David F Williams,Ewen J.C Kellar,David A Jesson,John F Watts

doi:10.1016/j.apsusc.2017.01.150

David F Williams, Ewen J.C Kellar + Show 2 more

Open Access

https://doi.org/10.1016/j.apsusc.2017.01.150

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Abstract

The surface of 316 stainless steel has been modified using cold atmospheric plasma (CAP) to increase the surface free energy (by cleaning the and chemically activating the surface)IN preparation for subsequent processes such as painting, coating or adhesive bonding. The analyses carried out, on CAP treated 316 stainless steel surfaces, includes X-ray photoelectron spectroscopy (XPS), imaging XPS (iXPS), and surface free energy (SFE) analysis using contact angle measurements.The CAP treatment is shown to increase the SFE of as-received 316 stainless steel from ∼39mJm−1 to >72mJm−1 after a short exposure to the plasma torch. This was found to correlate to a reduction in adventitious carbon, as determined by XPS analysis of the surface. The reduction from ∼90 at% to ∼30% and ∼39 at%, after being plasma treated for 5min and 15s respectively, shows that the process is relatively quick at changing the surface. It is suggested that the mechanism that causes the increase in surface free energy is chain scission of the hydrocarbon contamination triggered by free electrons in the plasma plume followed by chemical functionalisation of the metal oxide surface and some of the remaining carbon contamination layer.

Highlights

1.1 Pre-Treatment MethodsThe surface of a material is a critical feature to consider with regards to how it will interact with the surrounding environment
This paper describes work conducted using a variant of a cold atmospheric plasma (CAP) treatment, which has been used to treat 316 stainless steel
This shows that there is a small increase in the surface free energy when the surface is solvent wiped, which can be attributed to some of the upper layers of carbon contamination being removed

Summary

Introduction

1.1 Pre-Treatment MethodsThe surface of a material is a critical feature to consider with regards to how it will interact with the surrounding environment. The surface properties of a material can be modified by using different processes, which can be mechanical, energetic, chemical or a combination of these approaches each of these have its own advantages and disadvantages [1] Mechanical processes such as grit blasting or abrasion generally act to increase the rugosity of the surface, and they are relatively material independent processes. There is the danger that such adventitious material may be redeposited if abrasive media, (grit, wire brush bristles etc) is reused These processing methods are simplistic they are often effective in terms of enabling high initial bond strength and the equipment can beautomated and/or mounted on robots. While the equipment can be mounted on robots there is difficulty in quantifying the gritblasted surface: visual inspection is a common approach, but this adds to the cost and slows down the processing of a surface [2]

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