Does anyone have information on this process? How does it compare to hot dipped galvanizing and powder coating in terms of cost and performance?
James, is this like Sherardizing - http://en.wikipedia.org/wiki/Sherardizing?
Do you know the thickness and nature of the coating? I came across this in wikipedia as well:
Thermal diffusion galvanizing, a form of Sherardizing, provides a zinc coating on iron or copper based materials partially similar to hot dip galvanizing. The final surface is different than hot-dip Galvanizing; all of its zinc is alloyed. Zinc is applied in a powder form with “accelerator chemicals” (generally sand, but other chemicals are patented). The parts and the zinc powder are tumbled in a sealed drum while it is heated to slightly below zinc’s melting temperature. The drum must be heated evenly, or complications will arise. Due to the chemicals added to the zinc powder, the zinc/iron makes an alloy at a lower temperature than hot dip galvanizing. This process requires generally fewer preparatory cleanings than other methods. The dull-grey crystal structure formed by the process bonds stronger with paint, powder coating, and rubber overmolding processes than other methods. It is a preferred method for coating small, complex-shaped metals and smoothing in rough surfaces on items formed with powder metal.
It sounds like something that has become popular in Europe. If we can opt for powder-coating zinc to create a more stable alloy, rather than hot-dip zinc coating (galvanizing), and that alloy is easier to paint and more environmentally friendly, it may be a great find.
Warping of long lintels that are hot dipped galvanized has been a problem. It sounds like this might still be a problem with the thermal zinc coating.
Also I am curious if the treated products can be handled like galvanized steel with out fear of damaging the coating.
Thanks, Ken. I can get my mind around the concept now I need to try to figure out why my project owner’s rep wants to do this with hollow metal doors?
Richard, I would think the lower temperatures involved with “Sherardizing” would entail less warpage but I also am curious what size the largest member could be especially given the requirement for being “evenly heated.”
Just a guess; Thermal galvanizing might provide a heavier zinc coating since the frames are fabricated from electro galvanized sheet steel. Hot dip galvanizing would also not create a heavy coating, since the amount of zinc deposited is a function the thickness of the steel. I do not know if thermal galvanizing is dependent on the thickness of the steel.
Please let us know what you find out.
Here’s another thought, from cynical me: The Owner’s Rep is using the wrong words and doesn’t know what he’s talking about. Maybe he just wants thermally insulated doors with a galvanized coating?
Actually what the Owner’s Rep wants is explained here: http://www.steeldoor.org/tech_data.php See SDI 112. It’s the difference between Galvanized (great process for big steel items) vs. Galvannealed (easy to paint; no need to ‘pickle’ the zinc coating).
For those who participated in another thread about zinc-repair, here is something I stumbled across - http://www.galvanizeit.org/images/uploads/drGalv/Touch_Up_Methods_for_Galvanized_Steel.pdf
ASTM A780 still sounds like the way to go.
http://www.metallisation.com/process/
check this out. Thermally sprayed coatings, that are controllable and offer exceptional life expectancy. Sounds a promising solution.
[Note this website is in England with no US references observed. Colin]
As with so many technologies, this one seems to be one where Europe is way ahead of us. Note on the website that Guardo posted they even have ceramic coatings available. What a great option to have. Where do I sign up?