KnowledgeBase » Inspection

Weld Slag Clean Up Requirements for Galvanizing

When welded structures are hot-dip galvanized, the weld area cleanliness significantly affects the quality and appearance of the galvanized coating around the weld.  If a coated electrode (i.e. a flux-coated welding wire/rod/stick) is used during welding, all welding flux and slag must be cleaned prior to galvanizing or the ...
Continue Reading »

How to Clean Wet Storage Stain

Treatment of wet storage stain begins with drying the galvanized surface. As long as water remains on the zinc surface, and airflow is limited, the corrosion mechanism responsible for wet storage stain will continue, and can damage the zinc coating and underlying steel. After the galvanized surfaces are dried, the treatment processes differ dependi...
Continue Reading »

Who Is Responsible for Avoiding Embrittlement?

ASTM A143/A143M spells out who is responsible for avoiding embrittlement. The responsibility lies on the designer, fabricator, and the galvanizer, but each party has different responsibilities. Choosing steel appropriate for the practices normally encountered in the galvanizing process and designing the product to avoid embrittlement are the res...
Continue Reading »

Hydrogen Embrittlement

Hydrogen embrittlement occurs when steel cracks due to hydrogen that is trapped between the grains of the steel. Although steel commonly absorbs hydrogen during the hot-dip galvanizing process, it is usually expelled due to the temperature of the zinc in the galvanizing kettle. In some cases, however, the grain size of the steel is too small to a...
Continue Reading »

Methods to Reduce the Occurrence of Strain-Age Embrittlement

There are several ways to reduce the occurrence of strain-age embrittlement, but all methods focus on one aspect – reducing the stresses induced into the steel prior to galvanizing. Instead of cold working, which induces stresses into steel, the steel can be hot worked at temperatures between 1100F and 1300F. If it is necessary to cold work the steel,...
Continue Reading »

Is it possible to have steel with chemistry too good for galvanizing?

It is possible to have steel chemistry with levels of silicon and phosphorus that are too low to meet the minimum thickness levels specified in ASTM A123 and ASTM A153. Very low silicon levels are seen more often on pipe though, not plate because aluminum is sometimes used as a deoxider rather than silicon. For steel with very low levels of silicon and/or phos...
Continue Reading »

Wet Storage Stain vs. White Rust

Many people perceive wet storage stain to be the same as white rust and use the two terms interchangeably, but they do have distinct differences. Wet storage stain is the commonly known problem of white surface oxide formed on newly galvanized ste...
Continue Reading »

How to Prevent Wet Storage Stain

Prevention of wet storage stain includes not tightly stacking newly galvanized products on top of one another, removing standing water, and providing adequate air flow over the zinc surfaces. Newly galvanized articles should be stored under cover in dry and well ventilated...
Continue Reading »

Visual Observations for Finish and Appearance

The image to the right shows products with connected galvanized pieces that have different appearances. The appearances of these pieces differ greatly from one another due to the steel chemistry of the different sections of the parts; however, all of these products continue to have an equal amount of corrosion resistance throughout and meet the specification....
Continue Reading »

Reasons for Different Appearances

The amount of silicon added during the steel-making process can create differences in the appearance of galvanized products. The Sandelin Curve, as seen in the image to the left, compares zinc coating thickness to the mass percentage of silicon in the steel. The recommended silicon composition is either less than 0.04% or between 0.15% and 0.25%. Any steels not within these ranges are considered reactive steels and can be expected to form thic...
Continue Reading »

12345