Technical

Protection Against Rust and Corrosion

The presence of both oxygen and moisture on the metal surface is necessary for corrosion to occur and the exclusion of one or the other, or both, will prevent this reaction from occurring. Many other factors will contribute to the rate and severity of this chemical reaction such as residual matter, dust, remnants from previous processing operations and other impurities remaining on the metal surface. Therefore the removal of oxygen and moisture or the passivation of any moisture present combined with the removal of foreign matter on the metal surface are prerequisites to corrosion, free storage and shipment.

The following methods may be used to suppress metal corrosion.

1. Removal of moisture or the reduction in the relative humidity to below a critical level (below 50 Rh) through the use of an appropriate quanity of dessicants (silica gel being one ) in the surrounding environment.
2. Removal of air and moisture from the surrounding environment by replacing with nitrogen or other inert gas or drawing a vacuum.
3. The application of an impervious coating to the metal surface to prevent access by moisture and oxygen. Typical would be suitable rust preventative liquids, oils,greases and some polymer coatings to insulate the metal surface from the environment.
4. Passivating the action of moisture and oxygen present through the use of chemical inhibitors these generally work through the reaction of moisture present to prevent corrosion from occurring. These may be solids ,liquids or incorporated in a packaging medium such as paper or plastic film. The majority work through contact with the metal surface or in the vapour phase or both.

Cost effective protection in the storage and shipment of metal components

1. Ensure components to be protected are as free of contamination ,dirt and other impurities as possible.
2. Remove as much air as practicable from within the package .    
3. Exclude moisture bearing materials from within the package .cardboard may hold in excess of 12% of its weight in moisture. Green timber will increase the corrosion potential significantly through moisture content and acidity and should be excluded unless separated by physical barriers.

Selecting the most effective method of protection

Australian Inhibitor offers a range of VCI films and Papers, VCI emitters, Dessicants  rust preventative aerosols as well as liquids. VCI’s are particulary attractive since they are very effective and do not necissate the application and removal of  rust preventative coatings.

We will be delighted to provide whatever assistance may be required to achieve cost effective protection from corrosion for storage and transit.