Special coating protects Exico motors from corrosion

In the past it was common to accept the corrosion of motors and to constantly repaint them just to hide the rust - and in truth this practice is still used today in some areas. The problem with this approach is that once corrosion has started it tends to continue unless properly dealt with, leading to the early failure of the motors, possibly shortening their expected working life by a considerable margin.

Exico takes the view that prevention of corrosion in the first place is far better than cure after it has begun. This has led it to offering a range of protective coatings, along with advice on selection. Corrosion classifications according to EN ISO 12944-2 start with C1, which is typically in heated indoor applications such as offices and schools where the atmosphere is clean and dry so there is a very low corrosion risk.

It rises to C5 where permanent condensation and high levels of pollution make the corrosion risk very high. In fact C5 is split into C5-I for industrial and C5-M for marine because the two environments can be significantly different, particularly with respect to ambient salinity.

Class C4 also represents very demanding environments. Typically these will be in industries such as chemical manufacture and sewage processing, but can also include swimming pools, boat yards and inshore waterways. It is the highest class in which aluminium motors can be used, as they cannot be hot dip galvanised. Medium risk C3 classification covers urban applications and industrial uses where the presence of moisture and damaging pollutants is fairly low. C2 is a low risk category, which may be under cover or inside unheated buildings (unlikely to be outdoors), where contaminants are low but there is a risk of condensation due to temperature fluctuations.

To meet demanding environmental requirements, Exico's motors and parts (frames, end shields and terminal boxes) are specially treated. Cast iron parts are shot blasted to cleanliness level Sa 2.5 in accordance with EN ISO 8501-1, while steel parts are thoroughly cleaned and degreased by hand. All parts are then hot dip zinc galvanised before being primed with a special resin for protection against corrosive atmospheres.

Only once all parts are clean and treated does Exico assemble its motors, and once assembled they are cleaned again to remove all traces of grease, oil and other possible contaminants. After this, two coats of a two-part epoxy coating are applied to all external surfaces. All of this creates superb protection against corrosion, yet does not compromise the motors' ability to dissipate heat.

Exico recommends special coatings for all motors operating out of doors, indoors but exposed to direct sunlight, motors open to the weather (even if under cover) and in atmospheres where there may be acids or alkalis or aggressive compounds such as sulphur dioxide present.

It also notes that tropical installations may be subject to considerable humidity which can induce corrosion, so recommends protective coatings. Along the same lines non-tropical but humid environments such as swimming pools, spas, shower rooms, proving ovens, and industrial processes using steam or hot water require special consideration.

By using the guidance provided by EN ISO 12944-2 the environment operating conditions for a motor can be assessed and lead to an informed decision on the level of corrosion protection required. Finally a good rule of thumb will be that if you are uncertain, be cautious and move up to a higher C-classification rather than down to a lower one - any extra expense is likely to be repaid handsomely through greater longevity and reliability.

For more information about the company's motors with protective coatings go to www.exico.co.uk.