Reaching new heights on One World Trade Center Metco 16E spray system

The spire superstructure, fabricated by ADF Group Inc. in Terrebonne, Quebec, is comprised of seventeen individual sections that support a lighted beacon that can be seen over great distances, three communication rings and television broadcasting antennae. The total weight of the spire exceeds 680 metric tonnes (750 US tons).

When Drytec Trans-Canada, one of the most modern paint and grit blasting shops in Quebec and an Oerlikon Metco customer for years, was assigned as the contractor for the corrosion protection of the spire by the building’s primary owner, the Port Authority of New York and New Jersey, it soon became evident that the sheer size of the construction presented major challenges.

The original plan to galvanize the high-strength steel was dismissed as the immense size of the spire pieces, the varying thicknesses, and required double-dipping eliminated it as an option. Neither was painting a choice, as the binders in the paint systems would have compromised satellite communications. The Port Authority required pure zinc for conductivity and a final coating thickness of 10 to 20 mil (254 to 508 μm), which could not be achieved with paint. Nor could electric arc wire spray meet such a tightly controlled coating thickness requirement on the spire’s very complex geometry.

Drytec finally demonstrated flame spray technology to the Port Authority, and spent about a year testing flame spray equipment. Eventually, Drytec contacted Jacques Paradis, Key Account Manager at Oerlikon Metco, as they were facing major challenges — amongst them was the required coating specification bond strength of 700 psi (4.8 MPa).

Furthermore, Drytec had to qualify each operator to this spec before each shift, write a procedure and show the New York City inspector how they would mask the parts to prevent any overspray.

“After I met the New York City Inspector at the Drytec facility to demonstrate the Metco 16E wire combustion spray gun, and showed how to do the masking and spraying, he was absolutely convinced by the system”, recalls Jacques Paradis. As a result, the inspector recommended the Metco 16E system to Drytec to apply the zinc coating.

With this equipment, Drytec was able to achieve a bond strength of 1200 psi (8.3 MPa) on all parts of the antenna, thus meeting the required blast and thermal spray specifications, SSPC SP10 and SSPC-CS23, as well as the Port Authority’s adhesion test requirements, ISO 2063, and coating thickness of 10 to 20 mils (254 to 508 μm).

The inspector summarized his recommendation in very convincing words: ‘After a few years, I don’t want to go up there with a can of paint to do touch up! If any of your customers have doubt about the coating quality of the combustion wire spray gun, you can tell them the Word Trade Center Spire has been sprayed with a Metco 16E spray gun!’”, remembers Jacques Paradis smiling.