Tanks and tank farms are everywhere in the industrial world. Many tanks are used to store liquids. Others are used for mixing, dipping, or cleaning. Coatings are typically needed to protect the metal surfaces from rusting and provide a good appearance. Some environments demand more protection than others. It is therefore imperative to select the appropriate coatings system for specific tank conditions. The following examples provide guidelines for users of Cortec® Coatings.
Coating Outdoor Tanks
Surface prep prior to coating is imperative for any tank, especially those with rusty or dirty surfaces. Painters can either sandblast rusty surfaces to white metal or (in situations where this method is not preferred or allowed) remove loose rust and scale and then apply CorrVerter®, a water-based primer that converts the rust into a passive layer. Outdoor tanks usually need the most external protection because of exposure to rain, sun, and other harsh weather conditions. For tanks in these environments, Cortec® recommends priming tank exteriors with VpCI®-396 corrosion inhibiting primer followed by VpCI®-384 2K corrosion inhibiting topcoat. Using two coatings of VpCI®-396 primer instead of just one will add greater longevity to the system if the user has the time and budget to do so.
Storage tank internals have different requirements as they will not be exposed to much, if any, UV light, but they will be exposed to liquids. VpCI®-395 is a good choice for priming the interior walls and floors of many such storage tanks. This 2K epoxy coating brings corrosion inhibitors close to the metal surface and is good for immersion conditions. A nice advantage for workers applying VpCI®-395 in a semi-confined space is that it is water-based and has a low VOC of 0.2 lbs/gal (24 g/L). If desired, VpCI®-395 can be used as its own topcoat for extra durability since tank internals are typically not exposed to UV light. The recommended dry-film thickness (DFT) is 1.5-3.0 mils (37.5-75 µm) per coat.
Another important consideration for tank internals is the filling procedure. In many tanks, liquids are pumped in from the top. If the tank is large, the force of a liquid falling—for instance—50 feet (15 m) could chip the paint off the tank floor. Therefore, it is sometimes necessary to apply an 11.0-13.0 mil (275-325 µm) coat of VpCI®– 2026 over VpCI®-395 on the tank bottom for better impact resistance.
Coating Indoor Tanks
Indoor tanks are a different story because they are not exposed to sun or outdoor weather and often serve a different function than storage. Milder conditions make it easier to opt for a full water based-system, such as VpCI®-395 and EcoShield® VpCI®-386 for tank exteriors. As with outdoor tanks, adding a double coat of primer will help the coating system last longer and likely increase time between routine painting jobs. Mixing tanks at a manufacturing plant are often not coated internally; however, tanks that hold strong chemicals such as sulfuric acid may require a strong chemical resistant system such as VpCI®-395 and VpCI®-2026.
Ongoing Tank Maintenance
As with almost any industrial asset and fixture, tanks need special attention to keep them in good condition and protect them against sometimes harsh conditions. External and internal coating can be an important part of that routine maintenance both for appearance and metal preservation. Coating needs can vary from tank to tank, so be sure to contact Cortec® for specific recommendations on your application!
Keywords: tank coatings, corrosion protection, metal preservation, Cortec Coatings, tank maintenance, internal tank coatings, external tank coatings, rusty tank surface prep, chemical resistant coating, water-based coatings
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