Automotive industry moves towards greener pre-treatment chemistries

Globally, the automotive coatings market looks very good. Demand for is already very high, and by 2022 the market is expected to reach $27.69 billion. Increased car sales in developing countries, alongside new coating technologies, are ensuring suppliers of coatings and metal finishing processes will have plenty of opportunities in the years to come. However, a global tightening of environmental targets, including reducing energy and water usage, are going to spell change for the industry. One area that is already seeing widespread change is car pre-treatment conversion coatings. The industry is leaving phosphate-based coatings behind, and moving to zirconium and titanium-based chemistries.

The advantages of zirconium-based conversion coatings

Traditional iron and zinc phosphates are being replaced in many applications because zirconium-based coatings are better for the environment, cheaper to produce and easier to handle. Here’s a list of the main advantages of the alternative pre-treatment chemistry:

Uses less energy

Traditional iron-phosphate processing relies on heat; for the cleaning stage and for the coating stage itself. With zirconium, only the cleaning stage is heated; the coating is done at room temperature. This results in lower energy costs, and lowers the carbon footprint of the process.

Phosphate-free

The majority of zirconium-based products for pre-treatment do not contain phosphates. Phosphates are heavily legislated, and you can’t discharge waste containing significant amounts of them into public waste systems. Eliminating phosphates from the process also reduces the costs of hazardous waste disposal.

Very low coating weights

Coating weights of zirconium-based treatments are very low when compared with iron phosphate, and zinc phosphate. Typical thicknesses of the conversion coating are a few to hundreds of nanometres.

Less water use

A standard iron-phosphate process uses vast quantities of water for the rinsing stages and the evaporating stages. While still reliant on a fair amount of water, zirconium-based processes use far less as they use a counter-flow system for the rinsing stages.

Fewer hazardous substances

In addition to being phosphate-free, zirconium coatings do not contain hazardous substances, making them much safer for operators. Most zirconium coatings do not require accelerators, unlike zinc and iron phosphates that rely on accelerators to achieve a uniform coating.

Measurement of Zirconium thickness by XRF

A uniform thickness of the ultra-thin zirconium layer is essential for preventing corrosion, and providing a suitable surface for paint or coating layers. X-ray fluorescence (XRF) analysis is the best way to measure the thickness as it’s fast, accurate and non-destructive.

ASTM D7639 is the standard test method for measuring zirconium treatment weight or thickness on metal substrates by X-ray fluorescence. Hitachi’s X-MET8000 helps you conform to ASTM D7639, helping you create a process that is reliable and high quality.

The X-MET8000 is very easy to use. It’s a battery operated, hand-held XRF analyser within a robust, heavy-duty design that’s perfect for industrial applications, such as car coating pre-treatment processing. You simply ‘point and shoot’ with the instrument, and it will give you an accurate reading immediately. This makes it ideal for in-line analysis of coatweights during any stage of production. Another advantage of the X-MET8000 is that it doesn’t need a lot of sample preparation. Some XRF analysers need you to cut the sample, or acid-strip and then detect the amount of zirconium in the acidic solution. None of this is necessary with this piece of kit – simply place the nose directly against the panel to be measured and press the trigger. You’ll see the results on the screen within seconds.

 

For more information on how the X-MET7000 can help your processes, get in touch. Or, you can find more information here.

 




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Date: 8 July 2019

Author: Hitachi High-Tech Analytical Science

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