Best Possible Pretreatment
What is the best method for pretreatment on steel patio furniture?
Q. If you could choose only one method of pretreatment, chemical (or chemicals) of your choice or mechanical (sandblasting), for powder coating your personal set of brand new, bare, rust-free steel patio furniture, which would it be?—J.D.
A. Mechanical cleaning (abrasion) is a common way to prepare a part for coating. It has a great advantage over chemical cleaning because it promotes exceptional physical adhesion. The coating flows over a much larger surface area and into all the roughened areas created by the abrasion which holds it on tightly, providing the necessary adhesion—the first challenge to getting good performance. Chemical cleaning has a distinct advantage also. It does a much better job of removing organic (think oil) soils. It can also be used to apply a conversion coating, promoting adhesion and adding corrosion protection. Both methods have their place and both can work well on your furniture.
Now, to answer your question, what would I do with steel furniture? I would blast it, but there is an important proviso; you should use a two-coat process with one coat of zinc rich primer and then a good TGIC topcoat over that. If you use one layer of topcoat, I would go with zinc phosphate. Either method should work well. The zinc layer will protect the steel. I would not use iron phosphate and one coat of powder on steel for outdoor use. The initial adhesion will be good, but the corrosion protection is not good enough.
Find the follow up dialogue here.
Originally published in the August 2015 issue.
Infrared cure is gaining increased attention from coaters as a result of shorter cure cycles and the possibility of smaller floor space requirements when compared to convection oven curing.
How can you calculate the cost of powder coating a component if you only know its surface area? Powder coating expert Rodger Talbert has the answer.
Masking is employed in most any metal finishing operation where only a specifically defined area of the surface of a part must be exposed to a process. Conversely, masking may be employed on a surface where treatment is either not required or must be avoided. This article covers the many aspects of masking for metal finishing, including applications, methods and the various types of masking employed.