# Corrosion Treatment and Coating > Rust removal, surface profiling, zinc rich priming and undercoating on trailer frames, crossmembers and chassis structure. Source: https://fleetservicesocrv.com/services/trailer-and-chassis/corrosion-treatment-and-coating Business: Fleet Services OCRV, 23281 E La Palma Ave, Yorba Linda, CA 92887 Phone: (714) 909-1844. Serving Santa Ana, California, about 17 miles from the facility. Corrosion treatment and coating removes rust and oxidation from trailer and chassis structure, restores a clean profile, and rebuilds the protective film with primer, topcoat and cavity treatment. Work includes media blasting, hand and power tool cleaning, zinc rich priming, undercoating, drain path clearing and dissimilar metal isolation at aluminum to steel joints. ## Specification - Price range: $400 to $3,500 - Labor hours: 2 to 14 hours - Turnaround: Moderate body - Insurance: typically customer pay or fleet account ## Symptoms - Surface rust spreading from chips and coating breaks on the frame - Rust streaking running down from a crossmember to rail joint - White powdery crust building around aluminum rivet lines - Flaking or lifting coating that comes off in sheets - Scale buildup on crossmember tops visible through floor gaps - Water sitting in the bottom rail after washing rather than draining ## Why do trailers rust in Southern California? Fleet managers new to the region assume that no snow means no corrosion, and then they look under a ten year old trailer that has spent its life in Santa Ana and find crossmembers with holes in them. The driver is the marine layer. Coastal Orange County air carries chloride, and chloride does the same work to steel that road salt does, just more slowly and far more quietly. Washdown accelerates it. Food distribution, produce and beverage trailers get pressure washed constantly, and water that gets driven into a lapped joint or a box section does not come back out. Standing water inside a bottom rail or against the top of a crossmember is a continuous corrosion cell, and it works in exactly the places nobody can see without pulling a floor. The third source is galvanic. An aluminum skin fastened against a steel post, or a stainless fastener set directly into bare aluminum, forms a couple that corrodes the less noble metal at every contact point. On a trailer that means the aluminum around every fastener starts to powder and swell, and the classic tell is a rivet line that looks like it is growing white crust. - Chloride in coastal air acting on unprotected steel structure - Pressure wash water driven into lapped joints and box sections - Standing water on crossmember tops under a worn floor - Galvanic action at aluminum skin to steel post fastener lines - Plugged drain holes holding water in the bottom rail - Coating breaks from stone chip and yard contact exposing bare steel ## How is the surface prepared before anything gets sprayed? Preparation is the job. Coating over loose rust buys a season and then delaminates in sheets, taking the sound coating around it. Prep here follows recognized surface preparation practice: hand and power tool cleaning to remove loose scale and rust where access or adjacent components limit what can be done, and commercial media blasting where the area can be contained and the substrate can take it. Blasting does two things at once. It removes product down to sound metal and it leaves an anchor profile, the microscopic roughness that gives primer something to key into. A polished surface is a bad surface for coating. Profile is what turns a chemical bond into a mechanical one, and it is the single biggest difference between a coating that lasts eight years and one that lasts two. Where blasting is not practical, mechanical cleaning is combined with a rust converting treatment that reacts with remaining oxide to form a stable film. That is a legitimate tool in tight areas and a poor substitute for blasting on open structure. Any shop that offers converter as the whole answer on a badly corroded frame is selling a paint job, not a corrosion repair. ## What actually goes on the metal? The system is layered and each layer has a job. A two component epoxy primer goes on first at roughly 3 to 5 mils dry film thickness, and on badly exposed steel a zinc rich primer is used instead, carrying enough zinc in the dry film to provide sacrificial protection at any coating break. Zinc rich primer is the reason a chip in a properly coated frame does not turn into a rust bloom. Topcoat follows at roughly 2 to 4 mils, giving a total system in the 6 to 10 mil band on chassis structure. On the underside and on wheel path areas an undercoating goes over that, either a rubberized film that stays flexible under stone impact or an asphalt based product where abrasion resistance matters more than appearance. Product choice is matched to the surface, not applied uniformly because it is what is in the gun. Enclosed cavities get treated differently, because a film coating cannot reach inside a box section. Those areas get a creeping cavity wax injected through existing access points, which flows into lapped seams and displaces moisture. It is the least visible line item on the estimate and one of the highest value ones on a trailer that will stay in coastal service for another decade. - Two component epoxy primer at 3 to 5 mils dry film thickness - Zinc rich primer on exposed structural steel for sacrificial protection - Topcoat at 2 to 4 mils for a 6 to 10 mil total system on chassis - Rubberized or asphalt based undercoating on undersides and stone impact zones - Creeping cavity wax injected into box sections and lapped seams - Isolation tape or coating between aluminum and steel at every joint - Drain holes cleared and re-established so water leaves the structure ## When is the right time to coat a trailer? The single best moment is with the floor out. During a deck replacement the tops of every crossmember are exposed and reachable for the only time in that trailer's service life, and coating them then costs a fraction of what it would cost as a separate job. Any Santa Ana fleet doing a floor and skipping the coating line is leaving the best return on the table. The second best moment is right after a structural repair. Welding burns off coating well past the weld itself, and bare hot metal in coastal air starts oxidizing the same day. Repaired areas get prepped and coated as part of the repair here, but a fleet that has had weld work done elsewhere should get those areas treated before they sit through a rainy season. The worst time is when a crossmember already has a hole in it. At that point the conversation is structural repair, not coating, and no film thickness fixes missing section. Coating is preventive and restorative on sound metal, and fleet managers get the most out of it by putting units on a cycle rather than reacting to a failure. ## What does it cost and what should I expect it to do? Corrosion work carries the moderate body turnaround band, 4 to 8 business days, and the published range runs from roughly 400 dollars for a localized area up to about 3,500 dollars for full chassis and undercarriage treatment. Labor runs 2 to 14 hours. Body and paint labor bills at the posted 210 dollar rate, with materials calculated on the written estimate and a hazmat and disposal charge applying where chemicals are involved. What it does is buy time on sound metal, and the return depends entirely on the prep underneath. A properly blasted, primed and topcoated chassis in Santa Ana coastal service should hold up for the better part of a decade with periodic touch up at chip points. The same coating over a poorly prepared surface may not make it through three rainy seasons, which is why prep is not a place to shop price. For fleets running units in coastal Orange County, the practical approach is a cycle. Treat trailers on a rotating schedule rather than all at once, coordinate it with whatever else is bringing the unit up SR-55 and SR-91, and the fleet stays ahead of corrosion instead of paying for structural repairs that corrosion caused. ## Questions ### We are in Santa Ana, not the salt belt. Do I really need corrosion treatment? Yes, and it surprises fleets that move here. Coastal air carries chloride, which does the same work as road salt at a slower pace, and washdown water driven into joints keeps steel wet in places that never dry. Ten year old trailers in Santa Ana service routinely show crossmember section loss. It is quieter than salt belt corrosion, not absent. ### Can you just spray undercoating over the rust? No, and any shop that offers to is selling you a delay. Coating over loose rust traps moisture underneath and the film delaminates in sheets, usually taking the sound coating next to it. The rust gets removed down to sound metal with a proper profile first. That prep is most of the labor and all of the durability. ### What is the best time to do this on a trailer? With the floor out during a deck replacement. Crossmember tops are exposed and reachable exactly once in a trailer's life, and treating them then costs a fraction of doing it later. Second best is immediately after structural weld work, because welding burns off coating well past the bead and leaves bare hot metal in coastal air. ### How long will a coating system last? On a properly blasted, primed and topcoated chassis in Santa Ana coastal service, the better part of a decade with periodic touch up at chip points. Over marginal prep it can fail in a few seasons. The variable is almost never the product, it is the surface underneath it, which is why prep is the line item worth protecting in the budget. ### What is causing the white crust around my rivets? Galvanic corrosion at the aluminum to steel joint. The aluminum is the sacrificial metal in that pairing and it powders and swells at every contact point, which lifts the rivet head and looks like growth. The fix is isolating the two metals with tape or coating at the joint when the fastener line is renewed, not just cleaning the crust off. ### Do you treat inside the frame rails and box sections? Yes, with a creeping cavity wax injected through existing access points. Film coatings cannot reach inside a closed section, and closed sections are exactly where water collects. The wax flows into lapped seams, displaces moisture and stays soft so it keeps creeping. It is invisible on the finished unit and it is one of the highest value items on the estimate. ### Can this be done at the same time as body work? Yes, and it should be. Coating slots naturally into a body or floor job because the structure is already open and access is already established. For Santa Ana fleets it also avoids a second 17 mile trip up SR-55 and SR-91. Ask for the corrosion line on the estimate when you send the unit over for anything else.