Stainless steel is a tremendously versatile metal that is found in everyday life from parts in our automobiles to the flatware we eat with. Just like its many uses, stainless steel comes in many forms; the most common in our industry is AISI (American Iron and Steel Institute) classification 304 or Austenitic stainless steel, which is used for the manufacture of kitchen sinks and accessories. However, it is necessary to know not all 304 grade stainless steel products are equal and that is why it is important to understand the different classes of stainless steel that fall into the category of AISI grade 304.
Certainly, the most commonly used in sinks is 18/8 which means there is 18 percent chromium and 8 percent nickel by weight; there is also 18/10. The chromium creates a barrier, or passive film, to things like oxygen and moisture and against most corrosion, which is why it is called “stain-less” steel. This layer is very thin and invisible to the eye. When scratched it quickly reforms itself. The chromium content should be 18 percent to ensure adequate safeguards against rust. Equally as important is the nickel content, which ensures better resistance to stress-corrosion or cracking. Now that we understand what stainless steel is, let’s explore why rust can appear.
Most men can remember a time when they were in the shower shaving and they placed a can of shaving cream on the shower floor. More likely than not, over the course of just one day a ring of rust formed on the porcelain tile. How can that be when the tile doesn’t contain metal? Where does the rust come from? It comes from the can itself. Your tile doesn’t rust, but the rust is transferred from the can to the tile. The same can happen with a stainless steel sink.
Leaving a cast iron pot or pan in a sink can be problematic because it can leave iron particles that attach themselves to the sink. The best practice is to wash, dry and remove the pot from the sink right away. Also, leaving a vegetable or soup can in a sink can create the tell-tale rust ring.
After using the sink, it should be cleaned with the appropriate cleansers and then dried. This will aid in keeping foreign particles from attaching and causing the appearance of rust. Never use steel wool on a sink. It has a tendency to break apart and leave particles behind that can rust. Also, cleaners and abrasives allowed to dry on the surface of the sink can also degrade the finish.
Even in a new home or kitchen remodel where the sink has never been used, homeowners have discovered small areas of what appear to be rust stains scattered on a brand-new sink. They immediately blame the sink manufacturer for selling a bad sink. That is just plain WRONG. The real reason for these rust spots is because of an installation issue that sometimes gets overlooked. The rage in kitchens is natural stone or similar countertops. In order to fabricate the countertop to fit a kitchen, the installer uses a variety of tools such as drill bits and blades that are made of very hard steel and are sometimes even coated in industrial diamonds. Sometimes after the sink is mounted in a countertop, additional tweaking is needed to ensure that the radius or reveal of the sink is exactly perfect. In doing so, those same style bits and blades are used and, just like the steel wool we talked about earlier, these blades and bits also release small particles of foreign steel that can attach themselves to the surface of a sink and cause what appears to be surface rust. When these types of installations take place, installers should know to immediately clean the sink completely, but sometimes that just doesn’t happen and the customer is left with a sink that needs to be replaced.
Even with a perfect install, a sink that is properly cared for can all of a sudden show rust. It’s more than likely localized in an area near the drain, or at the side of the sink where the bowl meets the side. Where could this rust be coming from and why? Earlier in this article we spoke about the metal content of stainless steel and how there are certain levels of chromium and nickel needed to make sure a sink is resistant to corrosion. Well, there are standards for 304 stainless, but that doesn’t mean that all sinks are being made, especially in the last year, according to the regulations required by that certification.
The majority of stainless steel sinks are manufactured in China and the Chinese for the most part do a fantastic job at this process. However, the prices of steel were at all time highs over the last year, as was the cost of nickel, so some factories in China opted to use less nickel or replace the nickel with other alloys in order to make the same margins they were used to. The result was that some sink companies in the United States, who shop factories in China for the best prices instead of nurturing a longtime relationship with a factory, ended up with sink products that are below standard for 304 stainless steel. In fact, when the prices for steel were skyrocketing, there was a push from the Chinese manufacturers to make sinks out of 202 grade stainless. Several companies here in the United States did buy into that rationale and have been selling 202 grade stainless sinks in the marketplace. These sinks, because of the lower levels of chromium and nickel, are prone to corrosion and have caused a lot of controversy in the marketplace.
So, if you are selling and installing these sinks, you can expect to get calls for problems and either risking your reputation or replacing the sinks. A better option for the fabricator might be to seek out a sink supplier that has a solid relationship with a factory and can provide you with consistent, quality products at appropriate prices.