Handrail post (matl-Naval brass) which stands in a marine atmosphere needs to be coated with PVD. How much coat thickness in microns is needed?

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Vadim Verlotski Popular answer

There are two issues that make PVD coatings questionable in this application:

Corrosion protection is not guaranteed by PVD coating, regardless of whether it is 0.5 µm or 5 µm thick. These are much more decorative coatings that are not able to prevent corrosion of the substrate (brass) in a corrosive atmosphere. As a result of the subsurface corrosion, the layer can flake off.

PVD coatings on a soft substrate (brass) can easily be damaged by mechanical actions (impacts) because the substrate under the layer can deform plastically.

Simone Vezzù

surface roughness is the first element by my opinion to decide coating thickness especially if Line-of-sight technique Will be used as sputtering. Second, residual stress and risk of through thickness cracks. Generally, it is challenging to ho beyond 1-2 microns...

Vadim Verlotski

Mohammed Hussein j. H. Al'Atia

Dear Kezia Puvvula

it's not only challenging to decide on the coating thickness. The main challenge is with the brass itself since the stability and integrity of coating layer are very difficult to maintain during and after the PVD coating process as the vapor pressure of zinc in brass is high at the minimum operating temperature of PVD coater. The zinc evaporation causes the coating peel-off of and even incooperates the coating matrix and for that I agree with Dr. Vadim Verlotski

Best regards

Paul Lippens

PVD (sputter deposited) coatings are in practice (because of cost reasons) limited to 1-2 µm in thickness. For hard protective coatings you will need some kind of ion impingement upon the growing field (DC magnetron sputtering is not the right technique then), go for ion plating. Such ion plated coatings are corrosion resistant.

Kezia Puvvula

FIrstly, Thanks a lot on your replies.

I agree with Simone Vezzù on surface roughness as controlling the initial material catch up propencity in turn sliding friction. This should be carefully dealt upon to some extent. 1-2 microns -: will it sustain the weather conditions for long span is again dubious!!!

Vadim Verlotski and Mohammed Hussein j. H. Al'Atia , your suggestions triggered me to think in a new aspect. I missed this direction completely. Thank you so much. This seems to be a major issue. I will have to look deeply into it.

Heartfelt thanks, once again!!!

Paul Lippens , Does this IP coating stand on well?? Being an Amateur about this kind of coating, I feel interested to know more about this technique. As I start to think about PVD, number of questions on its endurance makes me think of an alternative. Its a great risk moving forward with PVD as this is not an experimentation work unfortunately.

Thanks for this Paul. Further suggestions on IP would be appreciated!!!

Ion plated coatings are very dense and usually have good adhesion to substrates. To further improve adhesion, you might want to effect a plasma pre treatment on the substrate.