In a previous post we analyzed the components of grades 304 and 316 stainless steel that make them rust resistant. Both contain chromium, and nickel and together these elements enable the outer surface of a casting to form a thin protective layer of chromium oxide that protects the lower surfaces and acts as a barrier to rust. However, only 316 stainless steel contains molybdenum which is a metal that specifically helps prevent rust caused by exposure to sea water or sodium chloride which is why this is the preferred steel for yachts and beach homes and why it is aptly described as marine grade stainless steel.
While 316 stainless steel in its production contains the necessary properties to prevent corrosion the thin nano thick protective film can be degraded and while the presence of nickel does help this layer self-heal and re-form the protective chromium oxide there may be occasions when the fixture will need to be treated.
Several years ago, we heard from a homeowner in Florida who reported that her 316 stainless steel handles was developing rust. On inspection we could see that sand and grease had adhered to the handle and it was these contaminants that were rusting. The handle itself was still sound and showed no structural decay, in other words, the steel was not actually rusting.
Morphic Entry Lever In 316 Stainless Steel Compare With Similar Handle After 10 Years In Image Below
This type of surface contamination can also occur when the stainless steel is machined especially if there are iron based metals in close proximity.
In both cases the surface can be cleaned or “passivated” by being immersed in a citric acid solution which will remove most contaminants and allow the surface to self-heal by forming a new passive layer of chromium oxide. I strongly recommend that you do not do this yourself but find a reputable passivation company in your area.
Morphic Entry Lever With Blue Powder Coat 10 Years After Installation
Marine grade steel is not only durable, but it polishes well and can be enhanced by using different finishing techniques or by adding color through powder coating. Powder coating is a durable way to add color to any stainless-steel fixture especially if it intended for outdoor use.