CrossLinker QXD™, in full

Technical detail

CrossLinker QXD™ is a penetrating primer system, and the word that matters in that description is penetrating. It does not sit on the surface as a tie coat waiting to be pulled off by whatever is bonded to it. It goes into the concrete and chemically bonds with it, which is what gives the finish coat above something bonded rather than something merely stuck.

Zirconia specifies it as the primer and bonding surface for the Fortress XD™ Balcony system, and it does the same job under compatible caulks, sealants and other topcoats. In place it also forms a moisture barrier that will not chalk, peel or delaminate. On the short form at the CrossLinker product page that is six words in a list. Here is what stands behind them.

What it is applied over

There are two approved substrates and no others: properly prepared dry concrete, or a dry and fully cured CeramycGuard™ surface. In both cases the surface has to be clear of oil, dust, grease, dirt, loose rust and any other foreign material before the first gallon is opened, because a chemical bond is still only as good as the face it is forming against.

Over CeramycGuard there is a readiness test that takes a minute and settles the question. Wipe several random areas with a clean, damp white rag. The rag should come away clean, or carrying only a very light residue. If CeramycGuard comes away on the rag, it is not cured yet: check that ambient temperature and humidity are inside the recommended application conditions, and give the coating another 24 hours. The CeramycGuard Technical Data Sheet covers that cure in more detail.

How it is applied

The target is a saturation coat, not a thin decorative film. Application is at 1 to 2 mils wet film thickness with a shed-free roller cover of 1/4 to 3/8 inch nap, laid down in a crosshatch pattern with 50 percent overlap. Coverage runs typically 300 to 400 or more square feet per gallon, and it moves with the porosity and the surface profile of the concrete rather than staying fixed.

Because the material is absorbing while it is being applied, the crew walks the floor in spiked shoes and reapplies wherever the surface has gone light or matted. That continues until uniform saturation of roughly 1 mil or more is maintained across the area. Uniform saturation is the finished condition to look for. A coverage figure met on paper while part of the slab drank more than its share is not the same thing.

Mask off anything that should stay uncoated, and plan a cut-in brush where an edge cannot be masked and concealed cleanly.

The windows that govern the job

CrossLinker QXD is time-governed at both ends, and the timing is the part most likely to cost a day if it is treated as advisory. Recoat with itself is 0 to 60 minutes. Fortress XD™, or any sealant, caulk or other compatible topcoat, goes on over a tack-free surface and within 2 hours.

Miss the topcoat window and the remedy is mechanical rather than chemical. The primer has to cure until the next day and then be sanded back down to concrete before the area is recoated. An existing topcoat edge can be lightly sanded so that fresh CrossLinker QXD, and the Fortress XD laid over it, feather into what is already down.

The same clock governs how much material to open. CrossLinker QXD ages quickly once the container is unsealed and should be used the same day, so on a job spanning more than one day the discipline is to open only what the remaining area needs. Material kept sealed can be reused the following day.

Conditions, drying and record keeping

The application window is 45°F to 85°F ambient with relative humidity between 20 and 85 percent. At 1 mil dry thickness and 50 percent relative humidity the material is dry to touch in 30 minutes at 55°F, 70°F and 85°F alike, and ready to topcoat in under 2 hours. Drying is dependent on temperature, humidity and film thickness, so treat that schedule as the shape of the day rather than a promise about it.

Zirconia recommends recording those conditions instead of estimating them. A HOBO MX 1101 or a similar logger, capturing temperature and humidity before, during and at the completion of the installation, is what later proves the curing conditions were actually met. On a warranty-relevant system that record is worth more than anyone's recollection of the weather.

Handling, storage and safety

Pot life is 1 year, and shelf life is 1 year from the date of delivery when the material is stored in its original unopened container, indoors, between 35°F and 100°F. Flash point is 14°F, so the product is stored and handled accordingly. Packaging is a 1 gallon unit (3.785 liter), which is the 300 to 400 square feet of coverage above. Sprayers and tools are cleaned thoroughly with acetone after application so no leftover material is left to set.

Read the Safety Data Sheet before use. Wear safety glasses, and gloves, a respirator or other protective equipment as needed to keep the material away from eyes, mouth, skin and other sensitive areas.

What this page deliberately does not claim

CrossLinker has one filed document, a Technical Data Sheet. No One-Sheet or Product Sheet has ever existed for it, so there is no performance percentage, no service-life figure and no third-party test result to publish here, and none is invented to fill the gap. What is above is the application data Zirconia publishes, written out in full. The performance story belongs to the layers on either side of it: CeramycGuard™ underneath and Fortress XD™ on top, each with its own documents.