Cleaning and Corrosion
Cleaning anodized aluminum is easy with the right technique. Because anodizing is so hard, you want to use an abrasive cleaning technique with a gentle soap. Do not use harsh acidic or alkaline cleaners because they may destroy the finish. Use solvents with care as they may stain the finish. Regardless of the technique, be sure to try a test area first. One recommended technique is to use an abrasive cleaning sponge with mild dishwashing liquid. Always test a small area first to prevent a widespread problem.
Metals are rated according to their “nobility.” When dissimilar metals are in contact with each other in the presence of oxygen and moisture, the more noble metal will corrode the less noble one. Contact between dissimilar metals should always be avoided. If contact cannot be avoided, the adjacent surfaces should be painted with bituminous paint or zinc chromate primers or paints. Taping or gasketing with non-absorptive materials is also effective.
Care should be taken to prevent the wash from copper alloy surfaces onto adjacent, exposed, less noble metal surfaces, since the traces of copper salts carried in the wash can accelerate the corrosion of less noble metals.
Stainless or stain resistant? Stainless steels contain at least 12% chromium and form a thin, invisible protective, corrosion-resistant, passive film on their surface. This film forms spontaneously when the chromium reacts with oxygen in air and water. If the film is damaged or removed during fabrication or polishing, it self-repairs immediately, so long as the surface is clean. If stainless steel corrodes, typically highly localized metal loss or pitting occurs – rarely general or uniform corrosion of the entire surface.
While problems with stainless products are infrequent, the name stainless can be somewhat misleading. It is not actually stainless, but stain resistant – it is a corrosion resistant alloy, not rustproof. Stainless steel may show some forms of corrosion and/or deterioration depending upon the degree of contaminants in its particular environment. Under certain conditions, it can rust unless a program of preventive maintenance is followed.
The environment in and around swimming pools and salt water contain salts which actively attack stainless steel. Heat and humidity increase the corrosive activity of chlorine and bromine salts. In addition, the corrosive action caused by salts that occurs from ice melting agents, such as calcium chloride and sodium chloride, can create the formation of rust. Other chemical reactions that can cause deterioration include carbon picked up from bending or fabricating tools, finishing equipment or steel covered work benches. It is also typical for contractors or masons to use muriatic acid solution on masonry – even the fumes from this liquid can attack stainless steel.
The material’s mechanical finish – satin or mirror – also plays a role in corrosion resistance. Corrosion-causing agents will collect in the fine lines of a satin finish as opposed to the smooth surface of a mirror finish.
Stainless steel is manufactured in various formats and can sometimes be selected to perform better in certain environments or applications. They are identified by T-304, T-316, etc. as well as L Grades (low carbon).
If you experience difficulty with your stainless products, it is likely that there is a contaminant in the environment. The first step is to identify the contaminant and to eliminate it. After that, assure that a preventive maintenance program is in place and being followed.
Stainless Steel Preventative Maintenance Suggestions
- Inspect the installation on a frequent schedule, taking note of discoloration and stains. Discoloration can and should be removed by cleaners recommended for stainless steel.
- Ongoing maintenance, consisting of a fresh water wash and wiping with a clean cloth, is recommended to minimize deterioration. In all but the most severe cases, this regular washing will eliminate the need for polishing.
- Note: Never use steel wool or harsh abrasive elements.