A line with spray painted parts was running smoothly except on Wednesdays when the paint would peel? Why only on Wednesdays? Mysteries of Science
Transcript
Northern Engraving a metal decorating plant, had a new production job for General Motors. Aluminum metal was cut, formed and painted to make tailgate panels.
The panels would be pressed into an attractive and more durable shape and then anodized to provide a protective finish.
The parts would then be spray painted with black letters and then the entire piece would be sprayed with clear lacquer. A new dedicated anodizing line was set up to handle the volume.
The job had been running for three days when suddenly on Wednesday the black urethane enamel sprayed to form letters began lifting off as the clear lacquer was sprayed on. Oil and grease were ruled out as being the problems.
The following day the paint looked fine and passed inspection everything was running smoothly until Wednesday of the following week, when the problem returned.
What was causing the paint to peal? Why was it only affected on Wednesdays?
Here's the rest of the story.
The aluminum that was processed on Wednesdays showed the presence of the chemical element silicone. These compounds are infamous for causing painting problems.
The silicate was either being added to the tank or getting through the high-tech water purifier. After some observations and testing the professor headed off to the water works of the small town. The water source was several deep artesian wells.
The main filters at the water works were cleaned every Wednesday. While the filters were cleaned the water works switched to an old well. The old well, located near a mineral quarry, was picking up silicate and the silicate went into the anodizing final sealing tank to end up on the parts before they were painted.
