How to choose the right coating for my project?
If one coating could do everything, coating selection would be limited to color and gloss choices and specification writing would be relatively simple. Since that magic coating does not (yet) exist, we are left with hundreds of selections to choose from. Many coatings will indeed perform multiple functions and are quite versatile in their many uses. These then become very popular. However real-world situations often demand more specific performance requirements that necessitate the selection of a more appropriate coating or coating system.
This article will address the key elements that influence coating selection. These elements will center around “needs” … Performance Needs, Application Needs, Budget Needs (Restrictions), and Other (Special) Needs. To uncover and define the “needs” we will approach the coating selection process through a series of four basic questions that the specifier, engineer or owner need to provide answers. Only in this way can the proper selection be made that will narrow down the hundreds of coating choices to the “best fit” options (assuming one exists). Sometimes however, the specific need or requirement exceeds the existing coating technology and compromises must be made to ensure a proper application.
What is being coated and why is it being coated?
The question sounds pretty basic, but answers can be surprisingly deceptive. In one example, the reason for painting a vessel could simply be because the CEO of the company is making a plant visit next month. Appearance then means everything and no one is really interested in the benefits of a 25-year corrosion resistant coating system. The answer to this question exposes the real reason for painting, the scope of the project and the expectations of the owner.
What exposure will the item see?
This is perhaps the real “meat and potatoes” question to be answered. It tells us what the real environment the coating will be exposed to. There are many parts to this question which include;
- Is the item exposed to an exterior (weathering, marine, industrial) environment or inside (mild, moderate or harsh exposures such as shower rooms or food process areas)?
- Are there any elevated temperature conditions?
- Are there any harsh chemical fumes or anticipated splash and spills of chemicals?
- Will the coating be covered up with insulation?
- Will there be any thermal cycling/shock?
- How frequent will the coating be cleaned and with what chemicals?
- Will the coating see any abrasion? What type (cutting or small particulate)?
- What is the existing condition of the substrate (new steel, contaminated steel, rusted steel, old coatings)?
- What is the condition of existing coatings?
How, when and where will the item be painted?
Answers to this question will define how the painting project will be handled logistically; whether shop applied, field applied or in-situ at an operating plant. It may uncover the need for a coating to handle early rain exposure or cold temperature cure. Certain coating systems will handle shop application better than others and will have less shipping damage to deal with later. If spraying the coating is not possible (overspray problems) then coatings that can be easily brush or rolled must be selected. If the speed of completion of the project is critical (most of course are) then fast dry/fast cure products will be preferred. In many operating plants, open abrasive blasting (for optimal service cleanliness and profile requirements) may not be possible. While this restriction is fairly common, products that have surface tolerant properties must be selected. And while these products are technologically advanced, products that require higher degrees of cleanliness are preferred for longer service lives. Compromises must be made depending on what can’t be done.
What are the owner’s expectation in terms of service life?
On its face value, one would think that the answer should be “as long as possible”. This is not always the case; especially with limited budgets. In the earlier case where the CEO was to visit the plant, the need to “freshen-up” a vessel could be done rather inexpensively using a coating system with a minimal design life at minimal cost. The argument makes even more sense if the vessel is to be dismantled in say 5 years. It makes no sense to select a 30-year paint system for that vessel. On the other hand, it may indeed make perfect sense to select a long-term service life system for say an elevated water tank with a design life of 90 years … and one that has the local high school mascot painted on its exterior. Long term corrosion protection and long term appearance are vitally important. In the end, one can choose a 3-5 year system, a 10-15 year system or a 25-30 year coating system. The longer service life systems will cost more in terms of material costs and labor (surface preparation and application).
In the end, it is best to discuss your coating needs with a coating professional; one that will walk you through the basic needs analysis outlined here and match the right coating system for your specific set of circumstances and expectations of service life.
to Resist Fuel Oil
There are three different Tnemec Coating Systems for Secondary Containment to resist Fuel Oil and/or a variety of other chemicals as follows
The 125-mil system is the best in that it is also the most abuse resistant. in that it can handle impact and heat shock. In addition to chemical and abuse resistance, due to the thickness of the system, it tends to compensate for sloppy installation of concrete floors and walls. It provides the thickness to cover joints and irregularity of CMU wall installation that frequently occurs in back of house areas like containment rooms.
Products such as Tnemec Series 215 Surfacing Epoxy and Tnemec Series 218 MortarClad are available to parge rough CMU walls and concrete walls and floors and to make transitions at inside corners at wall-to-wall and wall to floor intersections.
Moisture Vapor Transmission
In many facilities, the migration of moisture through the concrete slab prevents the use of traditional resinous flooring materials. Tnemec offers Series 241 Ultra-Tread MVT, a polyurethane modified concrete designed to reduce moisture vapor emissions prior to the application of non-breathing, polymer floor finishes. When used in conjunction with Tnemec’s ChemBloc systems, Series 241 Ultra-Tread MVT is installed underneath the secondary containment lining.
Storm Water Retention
Tnemec Series 262 Elasto-Shield® is an elastomeric coating that is applied at approximately 50 mils dry film thickness over concrete surfaces and serves as a waterproofing membrane with great flexibility (approximately 400% elongation). It is typically used in: storm retention, storm detention, gray water, fire water, cooling tower blow down and chiller water tanks. Series 264 is the potable water version of Series 262 that is used on potable water immersion.
The following describes the system:
Series 218 Mortarclad™ - Primer/filler/surfacer on concrete walls and floors (55-60 square feet per large kit (2.8 gallons) at 1/16" average thickness.
Series 215 Surfacing Epoxy - Alternate primer/filler/surface on concrete (30 square feet/gallon at 50 mils) or (15 square feet/gallon at 1/8" when filled with 210C sand).
Series 262 Elasto-Shield® - Elastomeric liner for walls and floors (approximately 20-25 square feet/gallon at total thickness of 55-60 mils or 45-55 square feet/gallon per coat when rolled on at 25 mils per coat). Available in black only.
Series 22 Epoxoline® - Epoxy primer/finish usually used on the underside of concrete ceilings to prevent water vapor from penetrating the concrete or to prevent rusting of rebar or chairs. Also used as a miscellaneous primer for steel and ductile iron prior to applying Series 262 (100 square feet/gallon per coat at 12-15 mils dft). Series 22 can also be used as an epoxy liner on walls and floors, either reinforced or unreinforced, depending on design parameters when 400% elongation is not required. Available in white. Series 22 is NSF certified.
Series V260 Tneme-Bond - Bonding agent for Series 262 or Series 264 Elasto-Shield® that is beyond recoat time or to make repairs at a later date. Use Series 260 Tneme-Bond, clear bonding primer, when you have to grind edge of cured Series 262 Elasto-Shield® to reapply more Series 262 Elasto-Shield®. Not needed during normal application process.
Series 265 Elasto-Shield® TG - Flexible caulk made from Series 262 Elasto-Shield® that occasionally may be required to fill small joints or serve as cant strip. It is normally applied in the range of 1/4“-3/8” thick and must be topcoated within 3-4 hours just like Series 262 Elasto-Sheild®.
Tnemec Series 394
PerimePrime is a primer developed by Tnemec to provide a practical solution for protecting steel at the perimeter of a building from rusting, and at the same time be compatible with a multitude of fireproofing products. In summary, Series 394 PerimePrime:
· Is a single pack, mio-zinc penetrating urethane primer for steel. No mixing is required.
· It is easy to apply, cures rapidly and will cure down as low as 20° F, depending on humidity. It must be applied at 35° F and rising.
· Has excellent corrosion resistance (10,000 hours salt fog, ASTM B117).
· Is a surface tolerant coating that can tolerate less than an SP-6. SP-3 is normally specified for steel behind the curtain wall/façade and can also be used outdoors; HOWEVER, is not as good as abrasive blasting.
· Is Slip Critical, even when applied over an SP-3.
· Can be applied in the shop or the field and can be top coated by a wide variety of coatings as well as fireproofing.
· Is compatible with many WR Grace and Isolatek products. Bond Tests per ASTM E 736 show compatibility with Grace, MK6, Z106, Z146 and Isolatek Type II and Cafco 300.
· Has UL Classification (File R21193, Project 02NK37526) for 3 hours and is compatible with ANY, UL classified spray applied fire resistive material having a max average density of 19.5 pcf. Has been tested in an actual burn at UL with Monokote MK-6 and Isolatek Type II. Webs up to 24” deep DO NOT require reinforcement.