Powder Coatings--6. Fault Correction

andrewfei

During the powder application process faults can occur,
as with any other process. Coated parts can develop
noticeable faults which places one or more quality
characteristic outside the usual tolerances, causing
items to be rejected.
If the part can not be utilised in a less critical or
sensitive situation it must be either repaired or
scrapped. The part should only be repaired if it is a
relatively easy and a cheap process. A small repair
could mean a simple touch-up, a more intensive repair
could be a complete re-coat. The decision to repair or
scrap the part is a matter of comparing total repair costs
versus total scrap costs. The scrapping costs would be
the addition of at least the material cost plus the total
variable product, storage and disposal cost.
In the case of a rework, costs incurred would be
(depending upon the nature of the fault) the sum of one
or more possible actions, such as touch up, sanding,
stripping, recoating or recurring. It is recommended to
test the selected working method at each stage in order
to ensure success.
Sanding - Contamination of the substrate surface
beneath the coating film which creates rough spots are
more difficult to repair. Sanding can be successful as
long as the sanding paper is carefully selected and
handled.
Touch-up - The repair of small defects, light spots or
hanger marks can easily be carried out with liquid
touch-up paint (applied by small brush or spray). The
selection of the correct touch-up material is critical.
The paint must be a perfect match with the already used
powder. Factors to be considered are:
1) Original specification of the coating film
2) Intended use or exposure
3) Chemistry of the powder and its curing process
4) Number of parts to be repaired
5) Time constraints.
Recoating - With powder coating it is possible to
apply a second coating layer on top of the first without
influencing the properties of the film. Confirmation
should be gained from the supplier. Recoating should
be carried out on the entire work-piece and not just part
of it, using the normal film thickness.
Double-curing - If a part is insufficiently cured it can
be oven cured a second time. A careful check of the
results is recommended before larger quantities are
handled this way. If in doubt ask your powder
supplier.
Stripping - In serious cases the entire first coating
layer must be removed by either chemicals, mechanical
methods or burn-off processes. After stripping it is
essential that the objects are cleaned and washed or
under go the complete pre-treatment process again
before recoating.

gerald

LZ, 多发点中文的吧，再说你的东西不够系统。。

gerald

LZ, 多发点中文的吧，再说你的东西不够系统。。