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Plymouth Tube’s Dry Lubricant Tube Coating

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Plymouth Tube Company’s dry lubricant tube coating, also known as C-Lube 10, is a sodium stearate (C18H35NaO2) soap that results in a dry, white lubricant that can be used to coat certain tubing materials. Sodium stearate is a fine, white powder that is commonly used as a stabilizer and thickener in soaps, deodorants, latex paints, rubbers, and inks. The chemical make up of sodium stearate is C18H35NaO2  , a long chain hydrocarbon which forms an aggregate of surfactant molecules to form a colloid suspension in water. The reaction that dry lube has with the zinc phosphate coating, a previous operation, at 170° F results in the lubrication coating. The coated tube will then consist of three coating layers which can be tested as components for a total coating weight.



Step 1: First, the bundled tubes are put into a sulfuric acid tank, which prepares the tubes for the lubricant process. This step is commonly known as the pickling process. During this step impurities such as rust, scale and other oxides are removed from the top layer of the tube to provide a clean surface for the zinc phosphate conversion coating (step 3).

Step 2: After the sulfuric acid tank, the bundle of steel tubes is lifted and dipped into the rinse tank which flushes out acid residue, solids and loose scale from the outer diameter (OD) and inner diameter (ID). 

Step 3: The steel tubes are then put into a phosphate tank, which coats the outside of the tube with crystalline zinc phosphate, which acts as a lubricant for the drawing process. This step acts as other pickling process.

Step 4: Since there may be some build up of iron or sludge, another quick rinse in a zinc phosphate rinse tank is required.

Step 5: Immediately following the rinse, the tubing enters a neutralizer tank containing nitrite borate, which removes the acidic phosphate solution and thoroughly prepares the surface for the lubricant. 

Step 6: The tube bundle is then lowered into a Lube tank with sodium stearate to act as the non-reactive lubricant.

Step 7:  Tubes are then laid on a drying table for a short period of time prior to inspection, fabricating, packing and shipping.  


Plymouth’s dry lubricant process has many advantages and benefits for manufacturers and fabricators. Most importantly, dry lubricant allows for a faster tube draw rate than oil. Dry lubricants can be more efficiently distributed on the surface of the tube and thus less lubricant is typically needed. The benefits are a cleaner and more environmentally friendly work area, as well as low health risk to workers due to the absence of vapors and mist used with as sprayed lubricant.  Additionally, a significant savings commensurate with the elimination of the costs associated with maintaining and operating a liquid lubricant system.

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