Parkerizing surface hardness

[andyfox1]

Hi all,

I've been through loads of Parkerizing suppliers' websites and cannot find any reference to the (Vickers) hardness of manganese phosphate surface coating. Can anyone point me in the right direction?

[I'm comparing a few different coatings on a thread that specifies MnP for corrosion and wear resistance, but I thought I'd have a look at some alternatives to see if there was anything better, as I figure that Parkerizing would be quite soft. I need to know what I am starting with in order to make a decent comparison...]

Cheers,

A.

 

[CoryPad]

Manganese phosphate is very soft. There is essentially no point in measuring hardness using a Vickers indenter.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

Andy,

We would like to help you, but as CoryPad mentioned, hardness testing of phosphate coatings is pointless. Can you provide some additional information on the application? In general, threaded fasteners are coated to reduce friction during tightening, not to provide additional hardness or wear resistance. Heat treating of fasteners provides the necessary microstructure to confer strength and wear resistance. Galling or other problems occur due to localized friction problems, not lack of wear resistance.

 

[Compositepro]

The hardness of soft coatings like paint is often tested for "pencil hardess". For example, 2H.

 

[JTreglio]

As noted in the previous posts, manganese phosphate is very soft and does not provide any wear resistance. If your need is for a corrosion and wear resistant surface, we have found (and patented) that it is possible to phosphate hard-coated steels. Essentially, we deposit a hard coating such as titanium nitride on the part surface. Because of pinholes in the coating (which are impossible to eliminate), the coating provides only marginal corrosion resistance even though it does not corrode. If the coated part is now put into the phosphate bath, the metal exposed in the pin holes is phosphated with no effect whatsoever on the coating itself. The phosphated surface at the bottom of the holes behaves normally, absorbing oil and providing corrosion resistance, but, being protected by the coating, which again does not corrode.

We have tested the process with titanium nitride, titanium aluminum nitride, and zirconium nitride, and with the first two coatings the corrosion resistance is comparable to that of the phosphated surface.

The surfaces coated with zirconium nitride are another story altogether. The coating itself provides substantial corrosion resistance, comparable to an oiled zinc phosphated surface. Coated/phosphated/oiled 1100 steel held up for 24 hours in ASTM B117 salt fog test with no visible rust, lasting much longer than the phosphated/oiled surface.

Jim Treglio