Stainless Steel - General Information

One of the advantages of stainless steel is its high resistance against environmental factors. However, this assumes proper protection and maintenance. This essay will tell you what you have to observe during basic and maintenance cleaning.

Dirt, effects of the weather and environmental factors demand a high degree of processing quality, cleaning and maintenance as a basic condition for a long durability of stainless steel. Cleaning has always been a tightrope walk between preserving the material and proper cleaning according to hygienic standards. The expected success will unfold only if the three factors cleaning agent, material and dirt are properly considered.

Use alkaline, acid or neutral agents for cleaning surfaces according to the kind and degree of dirt. Alkaline and—in case of slight dirt—neutral cleaning products help in particular to remove organic grease marks while limescale and corrosion residues are better eliminated by acid cleaners. Basic and maintenance cleaners are distinguished today by purpose and power. Regular maintenance cleaning is supposed to clean any dirt away and to prevent resistant scab and deposit from developing. Maintenance cleaners are expected to act quickly without damaging the basic substance.

Basic cleaners are used for intensive cleaning especially of resistant dirt and scab formations in more or less regular intervals. Basic cleaners are more aggressive against the basic substance but also provide more dirt—removing power.

Different corrosion phenomena may appear on stainless steel that more or less damage the basic substance: for example, flat, pitting, crack and stress corrosion or intergranular corrosion.

Corrosion may be initiated especially by aggressive, chloride—containing water. Using unsuitable cleaning agents, such as acid cleaners based on hydrochloric acid, may produce corrosion. If you are using stainless steel in contact with chloride—containing water then observe the highest permissible chloride values given by the manufacturer.

Too hard cleaning devices may scratch which will look unpleasant and invite more corrosion. Clean any weld seams with pickling pastes or cleaners so that a new passivation layer will develop.

Use alkaline, acid or neutral agents for cleaning surfaces according to the kind and degree of dirt. Alkaline and—in case of slight dirt—neutral cleaning products help in particular to remove organic grease marks while limescale and corrosion residues are better eliminated by acid cleaners. Basic and maintenance cleaners are distinguished today by purpose and power.

Regular maintenance cleaning is supposed to clean any dirt away and to prevent resistant scab and deposit from developing. Maintenance cleaners are expected to act quickly without damaging the basic substance.

Basic cleaners are used for intensive cleaning especially of resistant dirt and scab in more or less regular intervals. Basic cleaners are more aggressive against the basic substance but also provide more dirt— removing power.

Remove slight grease marks and inorganic deposits (lime, uric stone, surface rust) preferably with acid stainless steel cleaners. Combine suitable ingredients in the formulation to remove not only (surface) rust and lime but also grease films.

Capillary active compounds—surfactants—do not only cause the cleaner to moisten the cleaned surface completely and evenly, they also make sure that grease marks are dissolved and kept dissolved (emulsified). Adding alcohols and glycols may further enhance the degreasing effect of the surfactants. Lime (calcium carbonate) is dissolved by acids or acid salts. Furthermore, corrosion residues and surface rust deposits are removed by acid cleaning agents. Here, the dirt should be removed without damaging the metal.

However, hydrochloric acid or formic acid still used in building cleaning are entirely unsuitable because they cause severe corrosion and the blackening of stainless steel. Phosphoric acid is well suited. It is highly capable of dissolving lime and may combine with stainless steel to create a passivation layer. Furthermore, oxalic acid, nitric acid and hydrofluoric acid are also used in basic and acid cleaners. All three acids abrade much stronger, so that the metallic surface is uniformly cleaned. A new, as uniform passivation layer may develop, hence. These acids should be used only by specialists who observe the necessary safety measures, on account of their hazardous characteristics.

Since the acids may often undesirably damage the basic substance or leave an unprotected surface, corrosion inhibitors are integrated into the cleaning agents. They either create a physically bound protective layer or react chemically with the topmost metal layer so that a passivation layer will develop.

If organic dirt is very persistent, the use of alkaline cleaners may be necessary because they are able to emulsify grease marks by alkaline hydrolysis to make them 'soluble in water'. Alkaline cleaning agents contain chelating and sequestering agents which should not only prevent the deposition of lime but disperse pigment dirt and keep it dissolved. Alkaline cleaning solutions do not pose any danger to stainless steel.

Proper cleaning is not only a matter of the right cleaning agent at the right concentration but also depending on the factors temperature, time and mechanics. While the temperature for cleaning in swimming—pools is mostly set to ambient, cleaning agents, exposure and mechanical support may greatly vary.

When choosing the right mechanics (scrubber,pad, cleaning machines), consider that too hard cleaning devices may scratch: The destruction of the passivation layer and the resulting growth of the surface create a basis for corrosion. Hence, use only soft tools like bright pads, fleeces and sponges. The exposure depends on the type and degree of dirt. During the first or basic cleaning it may take several hours.

When stainless steel is welded, the seams will attract deposits like tinder or weld spatter. Preventing corrosion early on requires intensive first cleaning. Very powerful special products are used often that promote the development of a new closed passivation layer.

Such pickling cleaners or pastes may contain nitric acid and hydrofluoric acid as well which will make them accordingly aggressive. Even high concentrations may require several hours of exposure to remove all residues.

Stainless steel surfaces that are exposed to everyday effects of outdoors weather should be basically cleaned at regular intervals. A clean, metal pure surface is the prerequisite for the regeneration of the protecting passivation layer. This is achieved by using suitable basic cleaners or by highly concentrated maintenance cleaners.

If there is much dirt, it may be necessary to repeat the cleaning process. Suitable stainless steel cleaners should be used for the everyday cleaning of stainless steel surfaces. Use different thinners depending on the degree of dirt.

Not every stainless steel surface must be cleaned every day. That makes means of protection desirable which add to the passivation layer. Aggressive chlorine—containing water in particular should not be able to act on the surface, if possible. Appropriate waterproofing helps to make the water rapidly bead and run off. Maintenance oils may be used. Silicone—based maintenance oils mean better adhesion and, hence, have a longer effect, but their disadvantage is that they are hard to remove. Mineral oils in turn are easily removed with alkaline cleaners. Stainless steel surfaces do not provide fertile ground for micro—organisms. Nevertheless, regular disinfection of certain surfaces is compelling in the swimming— pool area, independent of the material. Modern disinfectants based on quaternary ammonium compounds do not mean a problem. Cleaning agents and disinfectants that contain chlorine or oxygen donors should be used only if they are followed by much rinsing with water.

Stainless steel needs maintenance and protection, the client of the metal builder wants to enjoy the advantages of the material for a long time. Modern stainless steel cleaners provide the possibility to remove slight organic dirt (grease films) as well as lime deposits and surface rust. They regenerate the passivation layer of stainless steel surfaces and preserve the 'natural' protective effect of the material. Alkaline cleaners are also able to remove severe organic dirt without damaging the material. Maintenance oils may additionally protect stainless steel surfaces.