Does your galvanizing not have a bright shiny appearance?

Often some galvanized articles do not have a perfect finish, they can be rough, lumpy, have cracks in pools of zinc or even be covered in white stains. This does not mean that they are in any way defective. In fact even if the appearance is not what you thought it would be, the protection that the coating offers is completely unaffected. Here below are some pictures of the more common surface blemishes with a description of what caused them. Please note however, that if the smoothness and/or the appearance of the finished article are important, please tell us when you are placing your order.

Please note that this page is provided for information only. Surface defects while they do occur are very rare in items we produce. This is down to our quality controlled processes. This quality controll is not just in the finished product, it is applied to every part of the galvanizing process and gives us far greater control over the occurunce of defects and because of this we have been able to virtually eliminate most of them.

Lumpiness. This is caused by uneven draining of zinc when it is removed from the bath. It also may be caused by the shape of the object not allowing the zinc to drain properly. The corrosion protection remains unaffected and the only reason why this would be rejected is if it was covered with sharp spikes of zinc which would make it dangerous to handle.

Roughness. A rough coating is normally caused by an uneven (or maybe an overly abundant) layering by alloy. This is normally caused by bad composition or surface condition of the substrate. This is nothing to be concerned about as an uneven surface is more often than not thicker than a normal coating. Sometimes however the surface may be substandard in as much that it could interfere with the intended use of the article.

Bare Patches. These are often nothing to worry about, as small bare areas are normally self healing due to the sacrificial nature of the coating. These can sometimes be caused by defects on the surface of the substrate (folds, impurities etc). If these bare patches are caused by faulty processing the item will be retreated as standard.

Flux and dirt. As we use flux in our dipping method residues occasionally adhere to the substrates surface. These residues when they come into contact with moisture can leave a white corrosion stain on the surface. More often than not this is just a surface blemish but it should be removed as a matter of course. Dirt may be picked up from anywhere and a gentle wash down is normally more than enough to remove it.

Pimples. This is normally caused by dross (zinc/iron residue found in the galvanizing bath) getting mixed in during the coating process, but it can also be caused by iron salts forming on the surface after cleaning. This effect is nothing to worry about as dross has much the same corrosion rate as pure zinc. The only time dross becomes a problem is when it appears in large amounts in the coating.

Wet Staining. This is a white corrosion product over a darker stain on the surface. It is normally caused by water being in contact with the surface for an extended period of time, this could be due to bad storage or any number of reasons. This should be removed if it is particularly heavy and a hard bristled brush is more than adequate for this job. If it is important that the finish stays bright the article can be treated with a barrier coating. Highland passivate all galvanizing to reduce this problem.

Dullness. This can happen where silicon has been added to the steel during manufacture. The reason for this is that because of the presence of the silicon the steel reacts quicker to the presence of zinc. This reaction continues after the article has been removed from the bath. So instead of an article being finished off with a layer of pure zinc, this layer has itself been converted to a steel/zinc alloy. These coatings tend to be thicker and longer lasting than standard.

Rust Staining. This is caused by the galvanized article coming into prolonged contact with an unprotected piece of steel. (e.g. untreated/painted bolts, water draining from unprotected steel, unprotected welds, etc). It should be noted that whereas it looks like the coating has failed, this is incorrect. This staining can be easily removed by using a scouring product or a wire brush. Occasionally when seen at a weld it is caused by weld porosity.