[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: FWD: Info: Request Powder Coating



Cleaning and pretreating with iron or zinc phosphate is essential to  insure
good adhesive and under-coating corrosion resistance in all organic coating
sysytems.    Handheld UV lamps - watch out for eye damage-  can be used to
inspect metal parts for cleanliness.  Under UV light, oils tend to be
phosphorescent and are easily visible on the metal surface .  The most common
"on the fly' test is the water break test.  A clean part should not exhibit  any
water brakes on the surface.  It should be sheeting evenly over the part.  If
oils are present, water breaks around the oily soils are easily seen.  It is a
good idea to insure that the metal part supplier is using a simple,  low
viscosity,  rust and oxidation (R&O) resistant oil.  They are readily removed
and free of problem ingredients such as silicone. Silicones anti foam additives
can be present in hydraulic oils, compressor oils and can cause big problems
(fish eyes) for a finisher.

Another problem that a finisher can encounter is "smut".  Smut is a carbonaceous
particle on the surface and is difficult to remove from metal surfaces because
it is electrostatically attached to the metals surface.   This smut is formed at
the  steel mill in annealing ovens or is just substandard grade of steel or
both. Some dumped steels are like this.  The smut gets intermingled with the
R&O oils from the steel mill, ( mill oils) , and remains on the surface after
cleaning.  Smut causes poor adhesion and poor corrosion resistance after
coating.   UV will not reveal it but a simple scotch tape test on the incoming
parts will.  The tape is applied to the incoming part, removed and placed on a
white piece of paper.  The carbon particles are then easily visible.