Fabricated metal items rusting on site

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Author Message Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 342 Registered: 01-2003 Posted on Friday, December 17, 2021 - 01:56 pm:    Have received a question I don't have a good answer for, hope ya'll can help me out: many metal fabrication items (columns for trellis, canopy supports) installed early on at jobsite were left outside with shop primer only and began to rust. Contractor did not want to paint them until the project was closer to done as the finish would likely be damaged by construction activities. Is there a way to control this in this spec? My first response was this is a sequencing issue. Is there a good way to protect these items short of the final finish when installed that would protect these items? anon (Unregistered Guest) Unregistered guest Posted on Friday, December 17, 2021 - 02:09 pm:    it would help if the primer were specified as zinc-rich and shop applied on commercial blast cleaned substrate (steel). topcoat can be applied in shop or in field with zinc-rich primer and proper application in shop. anything else will eventually result in coating failure (and rust). Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 343 Registered: 01-2003 Posted on Friday, December 17, 2021 - 02:46 pm:    Thanks, I think that will work out. David L. Heuring, AIA, CCCA Senior Member Username: daveh Post Number: 6 Registered: 04-2020 Posted on Friday, December 17, 2021 - 03:08 pm:    This is unfortunately a common occurrence on jobsites... Having the spec for the product/materials is one issue; having a spec dictating what we want in the performance of the work is another. I'd say, first, put something in the specification that requires a) protection of work partially installed that is impacted by weather conditions and b) completion of work where possible to prevent deterioration. Relative to the spec for products, in an area where metals are subjected to rusting, specify a wash primer- i.e. zinc chromate- be used prior to application of any coating- i.e. colored primer and finish coating. It is not the design team's responsibility to protect these items on the jobsite- it is the Contractors, so if they are damaged or corroded during construction, workmanship clauses in the specs should allow us to require these to be repaired or replaced. These conditions should always be noted on an observation field report. David L. Heuring, AIA, CCCA, LEED AP, NCARB Lisa Goodwin Robbins, RA, CCS, LEED ap Senior Member Username: lgoodrob Post Number: 400 Registered: 08-2004 Posted on Friday, December 17, 2021 - 03:57 pm:    Margaret, Doesn't the Contract make the GC/CM solely responsible for protection of work on site, whether stored or installed? - Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 344 Registered: 01-2003 Posted on Friday, December 17, 2021 - 04:38 pm:    Hi Lisa, Yes the GC is responsible to protecting installed work. The architect asked me to add some reinforcement as this has been a problem on previous projects with this builder/developer. anon (Unregistered Guest) Unregistered guest Posted on Friday, December 17, 2021 - 04:48 pm:    I cannot agree with David's recommendation that a "wash primer" be specified prior to coating application. Do not do this. Coatings are systems that include proper substrate preparation and application of the system's recommended primer and topcoat(s) for the type of system specified. Introducing a "wash primer" into a system that is not designed for this is a bad idea. The coating system will only be as durable as it has been specified. For plain steel the most durable coating is a shop-applied zinc primer over commercially blast cleaned steel and any number of compatible topcoats. All other coating systems will be far less durable and will fail much faster. I am working on a project right now in which exterior exposed steel beams were coated with an epoxy primer and acrylic topcoat. Looked just fine upon completion but just a couple of years after all of the steel beams are rusting. The coating system that was specified is simply inadequate. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 965 Registered: 10-2007 Posted on Friday, December 17, 2021 - 05:03 pm:    The items mentioned appear to be structural in nature. While the contractor would need to prepare the surface prior to applying the finish coat I do not believe there is a long-term problem in most cases. We are talking about a normally paced job. The rust may be noticeable, but it will have little impact. The rust will be relatively thin and thus the impact on section properties will be minimal. Note that on structural steel projects standard practice is not to apply a shop coat of paint to structural steel members, that will be exposed to the weather for several months. If the completed project will be subject to corrosive conditions a zinc rich shop coat may be appropriate. This is especially the case when there is a need for surface preparation that cannot be replicated in the field. anon (Unregistered Guest) Unregistered guest Posted on Friday, December 17, 2021 - 05:29 pm:    Agree that for structural considerations, surface rust appearing on exposed-to-weather trellis and canopy supports may not amount to anything of consequence (in the short term, anyway). But that is not the concern here, if I am understanding correctly. The concern is aesthetics. No Owner and no architect is happy with visible rust on these exposed structural elements when it appears. All of the problems stem from incorrect coating system specified and preparation. These elements are treated differently than garden-variety structural members exposed (or not exposed) to weather. They are often included in a separate Div 05 specification section "Architecturally Exposed Structural Steel (AESS)" and finish for this steel is also specified as distinctly different than other steel on the project. Note that the steel does not have to be specified as AESS to take advantage of superior coating systems discussed previously in this thread. David L. Heuring, AIA, CCCA Senior Member Username: daveh Post Number: 7 Registered: 04-2020 Posted on Friday, December 17, 2021 - 05:45 pm:    The issue of the wash primer is debated in the industry, but typically in areas where there is high humidity and salt air, metal with this type of preparation outlasts typical 2 and 3 coat systems. What isn't debatable is that if the primer does not adhere to the metal, it will separate and it doesn't matter what the finish coat is. So the bare metal does need to be prepped correctly based on the metal type and the finish coatings. The original question seemed to be can one control the Contractor's work sequencing, specifically to prevent and/or protect an installation that is partially complete and which because of this becomes damaged. Even if the prep was correct and the primer was good, primer coatings may get scratched, and installation of fasteners may wear the primer off. Where rust occurs, it can be removed. If it weakens the metal member or connection , it should be replaced. The spec can address these remedies by citing industry standards, specific instructions to repair, and unacceptable conditions. The Contractor is responsible for sequencing. The Design professional can reject Work that is not in conformance with the Contract Documents. Again, any of these types of on-site issues should be documented in an observation report and concerns discussed with the Design-Construction-Owner team. David L. Heuring, AIA, CCCA, LEED AP, NCARB Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 632 Registered: 10-2003 Posted on Saturday, December 18, 2021 - 03:40 pm:    Or.... saw intrinsically rust-resistant metal fabrications such as galvanized steel, stainless steel, aluminum, etc. Michael Chusid, RA FCSI CCS 1-818-219-4937 www.chusid.com www.buildingproduct.guru Paul Sweet (Unregistered Guest) Unregistered guest Posted on Monday, December 20, 2021 - 12:14 pm:    Columns for trellis & canopy supports sound like items that may be meant to be exposed. If this is for a spec you're working on, you could specify that they be stored inside or under cover, and to remove rust down to bare metal and re-prime. John Bunzick Senior Member Username: bunzick Post Number: 1866 Registered: 03-2002 Posted on Monday, December 20, 2021 - 03:25 pm:    It's my view that it is the generic shop primer where this is likeliest to occur. For structural steel that was to be concealed I never worried about it; basic shop primer was fine. And, fireproofing products will adhere to slightly rusted steel. But for anything that was exposed with another finish, I always specified a specific shop primer, sometimes by model number but usually by MPI number. This primer would be different depending on the top coat and whether interior or exterior, but there was a product listed that the structural steel fabricator had to use. It can get tricky for the fabricator to know which primer went where, so that had to be carefully thought out. Of course, for field-welding there had to be procedures for prep and painting of connections, too. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 966 Registered: 10-2007 Posted on Monday, December 20, 2021 - 05:00 pm:    Instead of specifying specific shop primer what about specifying SSPC standards which are apparently now provided by AMPP