• the steel supply company

Maskote Zinc Stop-Off

Factors

Some Things to Know

The performance of all steel coatings relies on proper surface preparation. Maskote Zinc Stop-Off is a durable solvent-based coating that will perform well under adverse conditions, however some attention to substrate and galvanizing conditions can result in improved performance.

Surface

Steel surface should be free of any impediments such as rust, as well as any oils, films or solvents left from the fabrication processes. Many solvents, including Saw Cut, Mineral Spirits, water based cutting oils, etc., leave a film of their own which may interfere with the coating adhering to the steel. 

  • Brush, wipe or wire wheel away any rust, flaking or debris.
  • Wipe the area to be coated clean with a rag soaked with MEK (Methyl Ethyl Ketone). In the case of threaded areas, a bristled brush soaked in MEK may be used to assure the thread cavities are thoroughly clean. 

Type of Steel

Maskote is proven successful on many grades and types of hot rolled carbon steel. If the steel involved is a unique alloy the fabricator should consider testing a piece to determine compatibility.

Temperature

As with all coatings extreme low temperatures will delay the curing time and this could affect performance.

Substrate Thickness (Mass)

The thickness of the steel being galvanized will effect the Hot Dip Galvanizing process. When steel is hot dip galvanized it is immersed in molten zinc. The immersion time is relative to the body of steel. Ideally the steel stays in the zinc until it reaches ambient temperature, approximately 840°F / 449°C. Once it is removed the larger the mass of steel, the longer it will take to cool down. Just as an example 1/2" diameter anchor bolts may cool to the touch in 10 minutes. 2" diameter anchor bolts may take one hour to cool to the same temperature. 

This will not stop Maskote from delivering positive results however the fabricator may find removal easier if the thickness of the coating is increased, or possibly two coats are applied in some cases. 

 

Zinc-Stop-Off

Removal Process

If an open, flat area is not properly prepared and coated and some Zinc adheres, it can be easily removed with a grinding wheel, sanding disc, flap disc, etc. On the other hand, if a bolt has zinc adhered in the threaded area it is much more difficult to correct. For this reason, the fabricator should pay extra attention to the surface preparation and consider 1) be sure to clean the threads thoroughly with MEK, 2) applying two coats of Maskote in situations where the repair is much more difficult.

Hot Dip Galvanizing Company

Standard to the structural and miscellaneous steel industry most commercial galvanizers follow ASTM Specifications A123 / A153. Within these procedures there will be variations, not only from one galvanizer to the next, but within one company from batch to batch. 

  • The acids used in the series of baths prior to galvanizing begin at full strength when first dispersed. As more new batches of steel are immersed they dilute the acid with contaminants. 
  • Similarly, through continued use the molten Zinc varies in composition and produces its own residue. 
  • The temperature of the molten Zinc bath will vary from day to day, especially in colder weather.
  • Cooling time will vary based on exterior temperature. Most commercial hot dip galvanizers work in open air factories and are subject to whatever the exterior temperature is. Winter temperatures can easily range from 50°F to 20°F in a matter of 24 hours.