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Stainless steel has long embellished the boat environment with bright chromed accents

  1 • Why is cleaning crucial?

Contrary to common understanding, stainless steel is neither a stainless material nor impervious to corrosion. For this reason there are over 200 stainless steel grades featuring different corrosion resistance levels and only some of them can be used for marine applications.

Regular cleaning is recommended and needed to preserve the good finish and corrosion resistance of stainless steel. Cleaning minimises the contamination of the surface areas as well as the risk of contamination of the surface with iron particles, also referred to as “suspended rust”.

In order to achieve optimal corrosion resistance, stainless steel undergoes a self-passivating process (see picture). 

Dirt accumulation might lead to a concentration of corrosive substances such as to damage the passive layer. Cleaning preserves the self-healing mechanism since it prevents critical concentrations of contaminants such as sulphur dioxide or chloride from causing ferrous contamination. For stainless steel the basic rule is ‘the cleaner, the better’ since none of its surface finishes can wear out. Maintenance frequency and costs of stainless steel are lower than those of many other materials and this makes up for the higher initial costs.

Stainless steel self-healing mechanism

The chrome content of the stainless steel alloy creates a thin clear passive layer on the surface. Despite thickness amounts to few atoms, the protective layer isolates the material from the surrounding environment and automatically repairs damage to itself in response to air or water. As a consequence, stainless steel is corrosion-resistant without the need of surface coating.

2 • Linkages

No galvanized parts shall be used to connect stainless steel parts. A galvanic reaction occurs in which the less noble metal corrodes rapidly and leaves rust stains on the noble metal. The galvanized part will break and rust stains will require extraordinary cleaning to be mended.

Stainless steel parts require only nuts and bolts of the same material

Iron dust contamination occurs when using tools or carrying out maintenance, cutting, boring and milling of stainless steel parts. Immediately remove the iron particles: they corrode quickly and attack the self-healing passive layer forming a type of corrosion known as pitting. When removing iron dust stains, proceed step by step depending on the extent of the problem and preventing contamination from spreading further:

  • In case of a surface stain or efflorescence, use non-abrasive pastes or polishers or apply a solution with a soft cloth or a cotton swab. Allow to react for some minutes without rubbing. This will remove iron dust without scratching or visibly altering the surface coat.
  • Use a detergent and proceed slowly and carefully when removing a small quantity of rust: in this way the material will be preserved.

3 • Frequency of cleaning

Cleaning of indoor stainless steel parts doesn’t differ from that of any other material since it has to be carried out before the surface is too dirty or covered with marks: cost and efforts will be reduced and the surface won’t be irrevocably scratched or damaged. Stainless steel is exposed to a wide range of pollutants potentially more aggressive, especially when it comes into contact with:

• The marine environment.

• Industrial pollutants.

• Air and transport pollution.

Cleaning frequency depends on aesthetic requirements and air corrosivity. When the highest level of cleanliness is required or in highly corrosive environments it is good practice to treat metal surfaces quite often. In case of exposure to highly polluting environments, increase frequency up to few months.

Maintenance cleaning and restoration cleaning

When preparing stainless steel claning specifications a distinction must be made between:

• Maintenance cleaning, which consists in removing dirt, scratches etc. from an unblemished stainless steel surface. The use of products like our Inox Cleaner 65.250.00 or 65.264.00 is recommended.

• Restoration cleaning, which consists in removing visible bleaching from stainless steel. Although stainless steel is intrinsically corrosion resistant, dark spots or localized corrosion are likely to appear normally due to two reasons:

  • ferrous dust deposits from carbon steel cutting, welding or grinding or due to the drainage of rusty water coming from other surfaces.
  • lack of maintenance causing the concentration of chlorides or other aggressive agents beyond the corrosion resistance limit of that particular type of steel.  The deposition of aggressive agents is due to seawater spraying, under which small cavities surrounded by a brown ring originate, called “tea spots”.

At this point, standard stain removers are useless while high abrasive Polishes such as 65.309.18 and 65.247.00 are highly recommended.

Protect what surrounds you as well as the environment!
Make sure you have a cover for the floor so as not to ruin your boat and avoid the solution drips into the sea.

Advice for those in charge with maintenance:
dos and don’ts

1 • Wipe in the direction of finishing and not transversely. Wipe from top to bottom overlapping subsequent surface passes.

2 • Do not use steel sponges or scrapers to remove stubborn stains.

3 • Do not use chlorine-based products such as bleach or strong acids (e.g. solvents).

4 • Rinse with plenty of tap water. If possible, dry thoroughly.

5 • Do not use chlorinated water for cleaning.

Marco Di Maio
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