All You Need to Know About Stripe Coatings

By: Tom Wunderlin, Induron Sales Representative

A stripe coat is defined as a coat of paint applied only to edges or welds on steel structures before or after a full coat is applied. The stripe coat is intended to give those areas sufficient film build to resist corrosion. Stripe coats also provide extra corrosion protection measures on edges, outside corners, crevices, bolt heads, fasteners, welds and other irregular surfaces.

What surfaces are typically stripe coated?  

Stripe coats are usually applied to crevices, nut and bolt assemblies, rivets, welds, inside/outside corners, corrosion pitted steel, built-up structural members and other irregularly shaped surfaces.

Why are these surfaces stripe coated?

These surfaces are stripe coated because they have edges and/or crevices that make it difficult to apply a uniform coat of paint. In these cases, coatings often get drawn away from the edges and become thin. Plus, it is not always possible to apply a coating to areas around nuts and bolts using spray while controlling thickness. To achieve evenness to the coating, brush striping is often used in these areas.

How are stripe coats applied?

Application by brush is the preferred method for applying stripe coats. Brush application forces the coating downward into crevices rather than bridging over them.  Airless or conventional spray can be used to apply the wet material, followed quickly by back brushing to work the coating in.  When properly done, spray application with back brushing provides good uniformity of the stripe coat.  Conventional spray may be preferred over airless spray for stripe coating because the applicator may have more control over the application process.

The stripe coat is commonly applied after a full primer coat to blast-cleaned steel. Applying a stripe coat before the full coat can make it easier to see the areas being stripe coated and is easily inspected.  Applying a stripe coat after a prime coat should employ the use of contrasting colors to make the stripe coat visible to applicators and inspectors.

When is it beneficial to apply a stripe coat?

The cost and labor associated with stripe coating is beneficial when the structure is immersion service, in a corrosive environment or includes complex structural configurations, such as rivets, flanges, etc.

Stripe coats are typically not specified to a finite wet film or dry film thickness because of irregularly shaped surfaces that may not be accurately measured with a dry film thickness gauge. The objective when applying stripe coats is to control the thickness, serve as a thin application and achieve complete and satisfactory coverage of the surface. Applying a stripe coat too thick may cause mud cracking, poor aesthetics or other defects.

Though stripe coating adds expense to a project, it is specified and performed when the extra service life provided outweighs the extra cost. Stripe coating is considered one of the most effective ways to avoid bridging, edge corrosion and breakdown of corners on a structure.

Are you interested in stripe coating? Contact Induron today!

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