How Do You Tell the Different Types of Rust on Steel Cargo Apart?

Steel starts to oxidise when it comes into contact with moisture and oxygen. This is a natural process, and some surface rust can be seen on almost any steel product stored in the open. What matters is the type and degree of rust, whether it affects the intended use of the product and when it formed.

Rust found at the discharge port that was not recorded before loading may be treated as having developed during carriage. Identifying and describing rust correctly during the pre-loading survey is therefore decisive for any later assessment.

Atmospheric rust is a thin, even layer, usually light brown to orange, formed by contact with humid air. It spreads across the surface without depth and may come away as a powder when wiped with a finger.

It is common on rebar, sections and uncoated plate stored in the open, and is often regarded as a normal characteristic of the product. Even so, describing it clearly in the report and in any remarks prevents misunderstandings later.

Rust from wetting forms when cargo comes into direct contact with water. It is darker, more irregular and patchier than atmospheric rust, and may show runs, rings or tide marks following the path where water flowed or pooled. On wrapped products, water trapped under the wrapping, staining of the inner wraps and drip marks are tell-tale signs.

In advanced cases, scaling, flaking and pitting may appear. Because this kind of rust can affect surface quality, it should be recorded item by item with its location.

White rust is a white or grey powdery oxidation product found on galvanised, zinc-coated steel. It forms particularly when moisture is trapped between tightly stacked galvanised sheets or coils with poor air circulation.

Because white rust can weaken the protective function of the coating, buyers may regard it as a significant defect. Even when unopened packages look sound from the outside, moisture marks at the package edges should be noted.

The source of wetting matters when responsibility is assessed. Fresh water from rain or condensation and seawater contact can point in different directions. On site, a simple chloride test with silver nitrate solution is widely used for an initial indication; a whitish precipitate forms where chlorides are present.

The test is only an indicator. A salty port atmosphere or residues from earlier handling can influence the result. Where a firm conclusion is needed, samples should be analysed in a laboratory and the test conditions recorded in the report.

Descriptions should rely on observable features rather than vague wording: which items, which part of the surface, how extensive and what it looks like. Photographs that show the item number and a reference for scale make the description easier to follow.

Storage conditions should be recorded too: whether the cargo was stored in the open or under cover, whether it was tarpaulined and what the recent rainfall has been. This information gives context to how the rust may have formed.

Describing rust type and degree relies on the on-site observation of a surveyor familiar with steel cargo. The surveyor reports on apparent condition rather than fitness for use; where a technical assessment is needed, it is referred to a specialist.

Karan Gözetim provides pre-loading surveys on steel cargo from its base in Gemlik; the scope of inspection and any testing are agreed at quotation stage.