Arc spraying: air quality requirements

[Stefan]

Dear SEF members,

What is your experience regarding compressed-air conditioning mainly for the arc spraying process? In our hobby workshop we are currently using a refrigerant dryer to clean the air for grit blasting and arc spraying. This should bring down the content of moisture, oil and dirt considerably, but the pressure dew point is still at 3 °C and a microfilter or an adsorption dryer of course would yield much cleaner air. So far, our coatings (Zn, Al, Cu base) are well-adhering (no bond strength measured), but I have no idea how big the quality gap is compared to the very best compressed-air quality. I also looked for scientific papers or reports, but couldn't find anything meaningful.
With a view to the costs, what kind of equipment is really useful and where could we make compromises?

Regards,

Stefan

[djewell]

As an arc spray equipment manufacturer, I recommend to my customers ISO 2.4.2 quality air. This is pretty easy to achieve without a lot of expensive equipment. This standard requires a 10 um filter, a 3 °C dewpoint, and 0.1 mg/m3 oil concentration. You should not need to make compromises to build a filtration system which fits your budget.

[Stefan]

Thank you for your answer. We're going to carry out some experiments to estimate the bond strength loss with our air quality compared to dry nitrogen.