Manufacturing engineers looking for stainless steel products want to know what type of stainless resists corrosion at different temperatures.
Stainless steel is not technically unable to stain or rust. Under low oxygen or high salinity (saltwater), it’s susceptible to corrosion. Various grades of stainless react differently, based on their chemical composition – how much carbon, chromium or nickel they contain. The chromium in stainless steel forms a film that blocks oxygen from corroding the steel surface. The result is “passivation,” which means the material is passive, not so active, when confronted by substances like air and water.
Temperature, fluids and stress on the structure can all spur corrosion. According to the McNally Institute website, the rate of corrosion attack doubles with every 18 F (10°C) rise in temperature. That can be caused by friction between parts as well. Continue reading →
Corrosion resistance of the two materials is not drastically different in mildly corrosive environments at ambient temperatures. In general, Grade 301 is a little less corrosion resistant than 304 because it has lower chromium and nickel content and higher carbon.
If 301 stainless is cut on a laser or welded, you’re more likely to see corrosion in the heat affected zones compared to 304 because of chromium carbide precipitation, which depletes the chromium in the heat affected areas. If the material is not regularly exposed to high temperatures, saltwater or other very corrosive conditions, 301 should be fine.
As a general rule, the smoother the surface, the less likely they are to experience corrosion. For example, cold rolled sheet metal or electropolished products will resist corrosion better than products with a brushed finish.
Yes. Marlin Steel can use nitrogen (at a 20 percent slower rate than stainless steel). However, it creates micro-cracking in the material. Depending on the client’s tolerances/specs, argon gas may be required to cut parts without micro-cracking in the material.
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Yes. Electropolishing of stainless steel is commonly used for food, drug, medical and semi-conductor applications and for those where high fatigue strength is needed. It removes burrs and sharp edges and lessens strains by removing microscopic nicks from the surface.
Sources: Professor Roger Wright of Rensselaer Polytechnic Institute; Dr. Jack Grubb of Allegheny Ludlum; Dr. William H. Cullen Jr. of the Nuclear Regulatory Commission and Dr. Shui Lee of Central Wire Industries; websites of AK Steel, Allegheny Technologies, Carpenter Technology, Sandmeyer Steel and Haward Corp.
Urethane (or more formally polyurethane) is an artificial polymer. As a protective coating on metal baskets, it is durable and very protective under UV rays. It is not great at inhibiting rust, but that is less a factor when coating rust-resistant material such as titanium, stainless steel or aluminum. The average coating thickness for urethane is 0.032” to 0.058”.