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Consider the following scenario, which points out one of the worst disappointments in the painting of steel structures.
The owner carefully plans a project to include a well-written specification, careful material evaluation and selection, a qualified contractor, and thorough inspection of the work. The project is done on time, within budget, and with no claims for extra work. Two years later, visual inspection of the project reveals that 99% of the painting work shows no signs of failure. Yet, essentially every edge, bolt, and weld is rusting.
What happened?
The project specification did not require "striping" or "stripe coating" of all edges and welds during the painting work. Is this the problem? Maybe...maybe not.
What is Striping' or 'Stripe Coating?'
A stripe coat is "a coat of paint applied only to edges or to welds on steel structures before or after a full coat is applied to the entire surface. The stripe coat is intended to give those areas sufficient film build to resist corrosion."1
Therefore, striping, as it is sometimes called, is the process of "painting the edges of a surface or welds to give them extra protection. Striping is done before priming or before tifie application of a full coat of paint."1
(In this article, the terms "stripe coating" and "striping" are used interchangeably.)
SSPC-PA 1, Shop, Field, and Maintenance Painting of Steel, includes the following advice about stripe coating.2
* If stripe coating is specified for a project, then all corners, crevices, rivets, bolts, welds, and sharp edges should receive a stripe coating with the priming paint before the steel receives a full coat of primer.
* The stripe coat should extend at least 1 in. (2 cm) from the edge.
* To prevent removal of the stripe coat by later application of the primer, the stripe coat should be allowed to set to touch before the full coat of primer is applied. (However, it should not be permitted to dry long enough to allow rusting of the unprimed steel.)
* Alternatively, the stripe coat may be applied after a complete coat of primer, especially if a long drying period for the stripe coat would allow the uncoated steel to deteriorate.
* Tinting of the stripe coat is advisable to promote contrast.