Originally Posted by
Bernice Loui
Difficulty and known problem with teflon coated metal surfaces that rub, the teflon coating will wear and over time disappear due to friction and abrasion. It is very difficult to hold tolerances required for a fluid seal for drawn and stamped metal parts. If the fit is too loose, the tank will leak, if the fit is too tight there will be difficult putting the parts together. To achieve a functional fit there must be some give in both of the parts involved to allow for tolerances and elasticity of the metal parts. Material thickness of the parts can make a very significant difference in the parts ability to be elastic enough yet springy enough to achieve a good fluid seal and allow for production tolerances.
Alternative would be to make the lid from a proper type of plastic. This is what Kindermann did in their developing tanks and they do not leak, hold up just fine over decades of servie, do not tent when dropped as metal parts will, and solves the problem of metal part tolerances and sealing.
Bernice
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