P. O. Box 815
Mansfield, Texas
76063
(817) 453-0704
TECHNICAL MEMO #12: Organizing a panel testing program.
One of the most frustrating experiences connected with operating a paint line is that of receiving notification that a test panel has failed salt spray testing, and realizing that you have no idea (and little chance of finding out) why. This usually results from inadequate information about line conditions at the time the panel was processed, and is complicated by the fact that a substantial amount of time has elapsed during testing. About all you know at this point is that there was, and may still be, some kind of problem. The most logical course of action is to re-run the tests to see whether there is still a problem, and if so, try to determine what it is. A properly designed panel testing program prevents this whole scenario from occurring, because it is structured to not only reveal the presence of a problem, but to give you an excellent chance of identifying the cause. Steps should be taken to insure that line conditions at the time test panels are run are a matter of record, and can be retrieved at a later date. A well-maintained log of the tests routinely run to maintain the washer is a basic part of good paint shop practice which is too valuable to neglect. Test panels should be run concurrently with a washer inspection (with results recorded) and submission of any appropriate bath samples for laboratory analysis. Other items which may be of value if maintained include such things as smoke charts on the ovens, records of chemical additions to the washer, a log of maintenance work done in the paint shop, and notes on any unusual conditions.
Care should be taken to insure that test panels can be identified after they are painted and tested. Good records will be wasted if the test panels can't be referenced back to them. Numbers or letters stamped into the panels is a common and effective way to mark panels, but should be applied before processing begins, or the resulting damage will affect the outcome of the tests.
The specific panel variations that are run can be structured so that conclusions can be drawn as to the reason for a test failure based upon which panels passed, and which failed. For example, if four panels are hung ahead of the washer and allowed to go through the washer and dryoff oven, one of these can be removed from the line for coating weight analysis, and replaced by a laboratory-prepared phosphated panel, producing the following variations:
A. One panel run through washer and dryoff only for coating weight analysis.
B. Three panels run through the complete plant paint system, one for salt spray testing and two for physical tests such as film thickness, pencil hardness, impact adhesion, mandrel bend, etc.
C. One panel with known-good metal preparation and plant paint to serve as a salt spray control panel.
In this example, if the salt spray panel described in "C" passes, while the one in "B" fails, one would suspect a washer problem. However, if both variations fail, paint would be a more likely suspect. Good records, careful thought, and intelligently-planned variations in testing can go a long way to insure that a panel testing program doesn't just tell you that something was wrong several weeks back, but also assists you in figuring out what it was.