STEEL-IT® 316 Stainless Steel Coating: Superior Protection
STEEL-IT® stainless steel based protective paint, is the highest performance alternative to zinc coatings, finishes, and zinc-rich paint. STEEL-IT provides a much tougher shield against corrosion, wear, abrasion, and UV. Choose your paint; get a free sample; find a distributor; or message us for information.
Zinc coatings come in numerous varieties and serve a range of useful purposes. But wherever an extra long-lasting, hard and durable, protective coating is necessary, STEEL-IT® is in many situations the more effective alternative to zinc-based options. STEEL-IT is infused with the no-nonsense resistance of a high-grade stainless steel. With is matte, industrial appearance and limited color choices, STEEL-IT lasts 10+ years in most environments, even in aggressive climates. Loaded to its solvent capacity with our proprietary 316L stainless steel micro-flake, STEEL-IT® polyurethane and epoxy coatings protect metal and nonporous materials (e.g. Masonite, wood, plastic, fiberglass). STEEL-IT is no less than 50% real stainless steel on drying. Our polyurethane coatings are weldable and UV-resistant. Nontoxic, STEEL-IT is USDA-approved as safe for accidental contact with food. Mindful of today’s environmental issues, we have also created a high-solids epoxy paint with low VOC levels, without sacrificing durability.
STEEL-IT® coatings preserve and enhance machinery, auto and equipment parts, metallic structures, and all manner of industrial surfaces. Select your STEEL-IT® coating; request a free sample; locate a distributor; or message us with a query!
STEEL-IT® vs. Zinc Paint: Compare & Contrast
Industry often opts for zinc paints and coatings where durability is called for. As an alternative to generic paints, zinc coatings display higher durability and higher resistance to rust and to certain types of corrosion. However, STEEL-IT is not your generic paint! Simply put, it is “Stainless Steel in a Can” and the market’s toughest protective coating. All heavy-duty paints depend on their chemistry for their protective properties. All details apart, in our case the choice is fundamentally between two metals: zinc on the one hand and 316L stainless steel on the other. Which is the more durable and resistant?
There are various types of zinc-enriched coatings and finishes, but they all depend on the chemical element Zinc (Zn) – a silvery white metal, the fourth most common metal in industry. Zinc is widely used as a particular type of anti-corrosion agent and as a galvanization coating for steel. Roughly one third of all the zinc produced today goes into making coatings used to galvanize other metals. Pure zinc hardly has a lot of practical uses. It is in many ways the opposite of stainless steel. A weak metal, Zinc has less than 50% of the tensile strength of mild carbon steel and has no place in load-bearing applications. Its low toughness makes it brittle, and though it can be increased by alloying with other metals, it is no match for the benefits 316 steel as the more powerful alternative. The most popular group of Zn alloys is named ZAMAK (an acronym of “zinc, aluminum, magnesium, and copper”). The best known Zn alloy is brass (55% minimum Cu), popular for its anticorrosive resistance. When zinc is exposed to air it naturally reacts to atmospheric carbon dioxide and forms a protective layer of zinc carbonate (chemical formula ZnCO3), which stops further reaction with the atmosphere and moisture.
But Zinc’s most distinctive protective advantage does not result from a special chemical toughness, but, on the contrary, from the metal’s reactivity, from its “sacrificial” behavior under corrosion. Zinc’s proneness to corrosion is an essential part of the corrosion protection mechanism realized by zinc coatings. Zinc, being anodic to iron and its alloys, corrodes “sacrificially” or “preferentially,” which means that it attracts all local oxidation to itself, thus protecting all the other metals present so long as it lasts. As a result, the steel substratum under the coating remains corrosion-free until the zinc, acting as a sacrificial anode, fully corrodes away. (This form of anticorrosive protection of metals is called “cathodic protection.”) One advantage of zinc and its alloys is that they are inexpensive relative to stainless steel; however, they are less strong.
316L stainless steel is, by contrast, exceptionally tough and durable. Characterized by outstanding mechanical and chemical resistance, it is one of the high-end stainless steel grades due to its strength and its resistant properties. Its high price is mostly caused by its high – 16-18% – chromium (Cr) content. (Chromium is more expensive than zinc.) It is the chromium that is the primary basis of stainless steel’s superior resistance. Thanks to it, the steel undergoes “passivation,” which means that the chromium in it reacts with atmospheric oxygen and forms an thin surface layer of chromium oxide, Cr2O3. It is chemically inert and instantly self-repairing when damaged (more chromium is oxidized). Similarly to the above-mentioned zinc carbonate layer in the case of a zinc surface, the Cr2O3 film on stainless steel acts as a protective shield, but its properties are far superior to ZnCO3. Hence the generally superior protective potential of STEEL-IT as zinc coatings alternative. By contrast with Zn coatings, STEEL-IT coatings completely rely entirely on barrier protection in their anticorrosive action. (STEEL-IT offers no galvanic protection per se.) Questions? Send us a message now!
Zinc Paints & Finishes: An Overview
There are several common kinds of zinc coatings, including the following:
- Zinc-rich Paints – mostly used as primers in 2- and 3-coat systems – are based on chemical solvents enriched with zinc. The solvent – either organic (epoxy and polyurethane binders) or inorganic (silicate binders) – is loaded with a high concentration of Zn dust. (A common example of an organic primer is a moisture-cured urethane zinc primer.) These paints have highly sacrificial anodic properties. Unlike regular protective paints, which work by creating a barrier layer between the underlying material and the environment, zinc rich primers give cathodic protection. Inorganic zinc-rich paints are somewhat better than organic ones at galvanic protection and abrasion resistance, but require more intensive surface preparation. Application is usually by air spray, but constant agitation of the paint is required to prevent the Zn particles from settling, and the feed line needs to be kept short. Application by brush or by roller is difficult, since the coat may become uneven, causing cracking where it is too thick.
- Galvanization. A zinc finish is applied electrochemically (electrogalvanizing) or in molten form by hot-dip galvanizing or spraying. As with other types of zinc coatings, the protective action of Zn galvanizing on ferrous alloys is double: (1) as a protective barrier against corrodents (while the zinc layer remains intact); (2) as a “sacrificial” coating: zinc protects iron while it lasts, by corroding ahead it. However, once corrosion has eaten away all the zinc it will attack the base metal. Electrolytic Zn plating provides rather poor corrosion protection. Moreover, galvanic zinc coatings on high-strength steel are subject to hydrogen embrittlement, especially when pickled with acids.
- Zinc Chromate (ZnCrO4) is a chemical that takes the form of a yellow powder or yellow-green crystals. It can be used in coatings and combines with other pigments for color variety. Now receding into history due to its discovered health and environmental hazards, it was used extensively in chromate conversion coatings. Zinc chromate was first produced by the Ford Motor Company in the 1920 and was used as a primer coating over ferrous metals or aluminum. (Historical examples include US civilian and military aircraft in the 1930s-50s and a range of aerospace and automotive applications. When used as a pigment, zinc chromate is nicknamed “zinc yellow” or “buttercup yellow.” Recent studies have revealed zinc chromate to be a health hazard. It is highly toxic and carcinogenic, which explains the drastic decline in its use in recent years.
- Zinc Flake Coatings, invented in the US in the 1970s and applied non-electrolytically for their anticorrosive quality, include a mixture of zinc and aluminum flakes combined and bonded within an inorganic matrix. There are three common types of zinc flake coatings: (1) those containing (carcinogenic) hexavalent chromium Cr(VI), now illegal in the countries of the European Council for application in the automotive and electrical industries, under legislation including the Vehicle End-of-Life Directive EC 2000/53 (2007) and directive EC 2002/95 on electrical and electronic equipment (RoHS). (Some other applications are still legal.) (2) Solvent-based Cr(VI)-free zinc flake coatings; and (3) waterborne Cr(VI)-free zinc flake coatings. The last two types are eco-friendly. Today, Cr(VI)-based Zn-flake coatings are completely gone from the auto industry. In the 1980-1990s, zinc-flake coating systems became popular in the automotive industry as an alternative to electroplating and especially as a coating for fasteners and other auto parts. They are also common in construction, electrical plants, and wind-power systems. The application of zinc flake coatings is complex. It requires special preparation of the coating, taking into account its temperature, viscosity, and stirring time. Zinc coatings are applicable by rack spraying; dip (items loaded in a basket are dipped into a container filled with the prepared coating; after dipping, the basket in spun so as to eliminate residue); rack-mounted dip-spinning (whereby items in baskets are dipped, spun and passed through a furnace on a rack). Surface preparation includes pickling with sulfuric or hydrochloric acid, which produces atomic hydrogen. However, pickling can make steel brittle. In order to avoid pickling procedures, other pre-treatment processes are required. An alternative to acid pickling that does not generate hydrogen is cleaning the surface with a water-based alkaline solution to remove oils and dirt, followed by blasting with tiny steel shot balls to remove any scaling and rust. When the liquid coat is sprayed on, it forms a uniform layer over the surface. Annealing (heating in an oven, followed by controlled slow cooling) is required for best results. Combined with pigments, these coatings offer attractive color choices.
Zinc coating types are not limited to the above. Here are some additional alternatives:
- Mechanical Zinc Plating– a plating method whereby small iron and steel components (
- Zinc Metallizing (Spraying). Zn wire or Zn dust is loaded into a heated gun and sprayed in molten form onto the abrasively cleaned target surface. The melted zinc is propelled by a combustion gas and/or compressed air to achieve the right velocity. A more recent variation on this method consists in feeding molten zinc directly into the spray nozzle. Metallizing works for surfaces of nearly any size.
These additional finish types have durability profiles and protection mechanisms similar to the other Zn coatings, due to their common fundamental ingredient – Zinc.
Differences Between STEEL-IT and Zinc Coatings
The protective mechanism of STEEL-IT is different from that of zinc coatings, due first and foremost to the fundamental chemical differences between Zinc and 316L Stainless Steel. The latter’s corrosion resistance has a different character due to its different place in the so called galvanic series. The galvanic or “electropotential” series characterizes the relative nobility / baseness of metals, semimetals, and alloys. When two different metals are placed in an electrolytic environment and are at the same connected by and external conductor, they will exhibit a difference in voltage potential. The baser element, which has a lower (i.e. “negative”) electrode potential, undergoes galvanic corrosion, acting as the electron-attracting anode and protecting the cathode. (Hence the term “cathodic protection.”)
The infographic figure representing the galvanic series clearly shows the relative positions of stainless steel and zinc in terms of their respective levels of galvanic corrodibility. As mentioned, zinc is a “base” metal and protects the coated substratum by corroding preferentially to it, i.e. ahead of it. Zinc corrodes sacrificially in combination with almost all other metals (magnesium being the one exception). As a 316L stainless steel based coating alternative, STEEL-IT protects the coated material simply by not corroding, or corroding at an exceptionally slow rate. (Only the precious metals are nobler – i.e. have higher corrosion resistance – than stainless steel, but they are also much more expensive).
We do not claim that STEEL-IT matches or exceeds every single protective advantage offered by zinc-based coatings and zinc-rich paints. Surely, zinc finishes have some specialized uses where STEEL-IT could not act as a legitimate substitute. One example are applications where cathodic protection is a must. In conditions of electrolytic submersion, STEEL-IT’s strong barrier protection potential can be an effective substitute for cathodic protection only if the STEEL-IT coat completely seals off the protected surface, so that galvanic (“bimetallic”) corrosion cannot occur because the coated metal has no contact with the electrolyte. But if the STEEL-IT coating is damaged and the coated metal comes into direct contact with the conductive solution, the metal will corrode galvanically, sometimes resulting in invisible but potentially devastating corrosion creep “behind the scenes” while the outer coating remains intact. In such contexts STEEL-IT may not be the perfect alternative to zinc-rich coatings. The use of a zinc-based paint rules such an eventuality even when it is compromised, because zinc will continue to corrode away preferentially to the nobler metal. Lastly, it is worth pointing out that some zinc coatings offer better high temperature performance than STEEL-IT.
On the whole, however, in many cases the STEEL-IT alternative offers a more advanced level of corrosion protection than zinc-rich paints, coatings, and other finishes. If in doubt, please review our SDS datasheets, or, if you need more information, you can save research time by sending us a direct message via the contact form.
What Our Customers Say
Says Jeff Proctor, Principal of Team Honda Ridgeline, “STEEL-IT ensures that we fulfill our responsibility to properly represent American Honda.”
Says Giannina Zapattini, Project Manager, Studio 804 Center for Architectural Design Research Project: With the exception of the STEEL-IT Epoxy System, none of these [other] products were able to offer the combination of reliable interior / exterior protection, flexibility, ease of application, high solids (required for LEED), and a steel-like finish.”
Says Chase Laven, Manager and Co-Driver, Bevly Wilson Racing Team: “STEEL-IT easily handles the abuse we put these trucks through each time we’re out on the racecourse.”
According to Ultimate Fabrication Inc., “In industrial refrigeration applications where our equipment faces temperature cycling ranging from 280°F down to -20°F we haven’t found a better coating system than STEEL-IT.”