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Fertilizer Resistance

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Farmers regularly fertilize their fields. This may involve adding phosphate or nitrogen-​based mineral fertilizer or organic fertilizers such as slurry or manure. However, some substances in fertilizers can increase corrosion of vehicles, machinery, and components. These include ammonia (NH3), ammonium nitrate (NH4NO3), urea ((NH2)2CO), potassium chloride (KCl), or calcium carbonate (lime, CaCO3). The result: rust on agricultural implements or tractors is commonplace and observed on bolts and chassis in a relatively short period of time.


Corrosion protection in agriculture is therefore faced with a challenge: not only is it necessary to protect against aggressive agents such as oxygen, but also against substances in fertilizers. In addition, protective coatings also need to withstand high mechanical stresses and be temperature resistant if installed near engines. Premium manufacturers are also placing increasing emphasis on the long-​term high-​grade appearance of their products. There is no national / international standard or other generally-​recognized regulation for the testing of fertilizer resistance of coatings.

Today, many coatings with multi-​layer structures are applied to components for vehicles and machinery used in agriculture. Phosphate and varnish are applied, electroplating and hot-​dip galvanizing are utilized, as well as powder coatings. In vehicles, the protective coating usually consists of two coating materials: an electrolytically-​applied coating (keyword: cathodic dip coating, E-Coat) and a powder coating. This combination provides passive protection against corrosion. If these coatings are damaged, components can rapidly begin to rust.

There is also another approach: studies show that multi-​coat systems containing zinc flakes provide better protection against corrosive agents such as fertilizers than the combination of  E-coat and powder coating. This multi-​layer system with good fertilizer resistance usually comprises two layers. The base coat layer contains zinc and aluminum flakes. These flakes provide active protection (i.e. cathodic corrosion protection) of the component against corrosive agents (e.g. as oxygen and moisture). The arrangement of the flakes also results in a barrier effect that slows attacks by corrosive media.

The topcoat consists of an organic or inorganic material depending on the requirements of the application. The topcoat protects against chemicals such as acids and alkalis as well as aggressive substances such as fertilizer.

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Technical terms cannot always be avoided. As corrosion experts, we not only want to give you comprehensive advice, we are also interested in making you a corrosion expert yourself.

The variety around the topic of corrosion and corrosion protection is also in our glossary at home: explanations from A as in Adhesion to T as in Thread tolerance. Have fun clicking through!