Zinc, zinc-nickel, nickel, tin, silver, gold and cadmium, run to print in Texas since 1979. This page is the decision rather than the definition — which deposit, rack or barrel, how much it builds, and which plant runs it.
Most plating callouts get written backwards. Someone picks a metal, then finds the thread will not gauge, or that the coating was never going to survive the environment. The metal is the last decision.
What is underneath. Aluminum needs a zincate before anything will hold. Stainless needs its passive oxide stripped and activated. Castings and sintered parts hold solution in their porosity and bleed it back later. The substrate sets the front end of the process.
Sacrificial or barrier. This decides whether a scratch matters. Zinc, zinc-nickel and cadmium are anodic to steel — they corrode first and protect the steel around a scratch. Nickel, tin, silver and gold are barriers and cathodic to steel, so a pore concentrates corrosion at that one point instead of spreading it. A barrier coating on steel has to be continuous to work at all.
Environment and temperature. Dry indoor service is a different specification from road salt, marine air or a daily alkaline wash. Sustained heat sorts the field fast: zinc loses ground, silver and gold do not.
Electrical or joining function. Solderability, contact resistance, RF surface conductivity, wire bonding and torque control each push toward a different deposit, and some rule out a chromate entirely.
Dimensional budget. How much can the critical feature grow before it is scrap. If the answer is nothing, that belongs on the drawing, not in a rejection report.
The physics is simple: the part is the cathode, current reduces dissolved metal onto its surface, and thickness is current density multiplied by time. Current density is never uniform on a real part — edges and corners run hot, recesses and bores run cold — and nearly everything below follows from that. The exception is electroless nickel, deposited by chemical reaction with no current, which lands at the same thickness in a blind hole as on an outside corner. To compare plating against the alternatives, start with types of metal plating and finishing.
Before chemistry, the part decides how it is held. Geometry, weight, thread presence and cosmetic requirement settle it, and the answer changes both the price and the thickness distribution.
Barrel: parts go loose into a rotating perforated drum and make contact by tumbling. Nobody handles an individual part. It is the cheapest way to plate small hardware in volume. Rack: each part is fixtured in a fixed position relative to the anodes, so you can control orientation, shield a hot edge, add a thief, and drive current into a recess a barrel would never reach. You pay for the loading labor, and every contact point leaves a mark.
| Factor | Points to barrel | Points to rack |
|---|---|---|
| Size and weight | Small, light, robust parts that survive tumbling | Large or heavy parts, or anything that dents itself |
| Geometry | Simple shapes that do not nest, tangle or cup | Deep recesses, blind bores, long tubes, flat plates that stack |
| Threads | Coarse threads on ordinary hardware | Fine or critical threads, anything gauged after plating |
| Cosmetics | No appearance requirement; tumbling marks acceptable | Visible surfaces, bright finishes, scratch-inspected parts |
| Thickness control | Averaged by tumbling; thinner deposit, longer cycle | Controllable, with edge build-up and contact marks |
| Quantity | High volume, low value per piece | Low volume, high value per piece, or long parts |
Two consequences worth designing for. A rack leaves rack marks — thin or unplated contact points where the fixture held the part. They are unavoidable, so tell us where they are allowed to be; if the drawing is silent we will choose, and it may not be where you would have. And a barrel averages thickness across the load but runs thin in the deepest recesses. If a bore or counterbore carries a thickness minimum, it usually wants a rack.
Delicate, sharp-edged, magnetised or interlocking parts look like barrel candidates on paper and are not. Send the print before committing a production quantity.
Every family below runs at Gleco. What follows is what an engineer actually picks each one for.
Chosen when steel needs sacrificial protection at the lowest cost per part — fasteners, brackets, stampings, enclosures. Normally called to ASTM B633 with a service condition and a chromate type. Start at zinc plating, then pick the bath: alkaline zinc throws better into recesses and deposits more evenly on complex parts; chloride (acid) zinc plates faster, runs brighter, and handles cast iron and hardened steel that alkaline struggles with.
Chosen when zinc is not enough. Still sacrificial to steel, but it corrodes far more slowly, survives sustained heat far better, and sits close enough to aluminum galvanically to bolt the two together. It is the usual route when a legacy cadmium print has to be converted — zinc-nickel versus cadmium covers that trade honestly. ASTM B841, AMS 2417. See zinc-nickel plating.
Chosen as a hard barrier layer, as the undercoat that stops base-metal diffusion beneath silver or gold, and for wear and build-up on repairable parts. QQ-N-290, AMS 2403. Bright nickel is the same family with brighteners in the bath, chosen when appearance is part of the requirement and paid for in higher internal stress. See nickel plating.
Chosen when the deposit must be thick and low-stress: dimensional restoration and salvage, electroforming, and undercoats that will later be brazed or welded. The sulfamate bath gives a ductile, nearly stress-free deposit that builds far beyond what a Watts nickel tolerates. AMS 2424, MIL-P-27418. Sulfamate nickel runs at the McAllen plant.
Chosen for geometry. Deposited chemically rather than by current, it holds the same thickness inside a blind hole, down a bore and on a sharp corner — which makes it the practical choice for hydraulic bodies, manifolds and internal passages with a thickness minimum. Phosphorus content is the real specification: low phos runs harder, high phos runs more corrosion resistant and is effectively non-magnetic as deposited. ASTM B733 and AMS 2404, with MIL-C-26074 still on legacy prints. See electroless nickel plating and the ASTM B733 reference.
Chosen for solderability and for a soft, conductive barrier on copper, brass and steel. Matte tin is the electronics default because a matte deposit is markedly less prone to tin whiskers than a bright one, which matters wherever conductor spacing is fine. Bright tin wins where appearance or a smoother contact surface does. ASTM B545, MIL-T-10727, AMS 2408. Overview at tin plating. Matte tin runs at Rowlett.
Chosen for the lowest contact resistance of any practical plated finish, for RF surface conductivity, for high-temperature electrical joints, and as an anti-galling and bearing surface on threaded steel. Appearance is the classification — QQ-S-365 Type I matte, II semi-bright, III bright; ASTM B700 separates purity from appearance. Pick matte silver for bearing and anti-galling work, semi-bright silver as the general electrical compromise, bright silver where reflectivity is called out. Start at silver plating. Bright and semi-bright silver run at McAllen.
Chosen when a contact has to stay reliable for the life of the part. Gold forms no insulating oxide, so contact resistance stays stable at the low currents and voltages where a tarnished surface simply stops conducting. It is also the finish for wire bonding and hermetic sealing surfaces. Expensive, so it is specified thin, over a nickel barrier, and only where it is needed. ASTM B488, MIL-DTL-45204. Gold plating runs at the McAllen plant.
Chosen almost entirely because the print says so — and the print says so for three reasons that are hard to replace at once: cadmium is galvanically quiet against aluminum, naturally lubricious so torque-tension behavior is predictable, and it performs in salt. It is a controlled material with real handling obligations. AMS-QQ-P-416. See cadmium plating, the AMS-QQ-P-416 reference, or cadmium plating for Dallas work. McAllen only.
Not offered as a standalone finish. Copper runs only as an undercoat — a levelling and adhesion layer beneath nickel, tin, silver or gold. If your print calls copper as the final surface, tell us what the copper is meant to do and we will tell you which stack does it.
If the part is aluminum and the requirement is hardness rather than conductivity, the answer is usually not plating — see anodizing, or Type III hardcoat for wear surfaces. If it is stainless and the requirement is corrosion resistance, it is often passivation rather than a deposit.
Plating adds material. That sentence causes more rejected lots than any chemistry problem, because it is obvious in isolation and easy to forget on a drawing.
On a flat face the deposit adds its own thickness. On a shaft or a bore it adds twice that to the diameter, because it lands on both sides. On a 60° thread the rule of thumb is that pitch diameter grows by roughly four times the plating thickness — so a deposit that sounds negligible on a face takes a thread straight out of class. Threaded parts gauged after plating must be machined to a before-plating limit, and the drawing has to say which.
Current density is highest at edges, corners and external threads, so a rack-plated part carries more deposit there than mid-face: the minimum is met somewhere thin and the maximum is threatened somewhere sharp. Press fits, bearing bores, dowel holes and sealing faces either get masked or get dimensioned to accept the build. Where thickness must be predictable regardless of geometry, electroless nickel behaves; where a thick low-stress build is the goal, sulfamate nickel is designed for it.
Mark three things and most first-article back-and-forth disappears: the surfaces that must not be plated, the surfaces that must hold a thickness minimum, and the surfaces where a rack contact mark is acceptable. The design guide covers masking, thickness callouts and thread allowances in detail.
Adhesion failures are almost never plating failures. They are cleaning failures that showed up later.
Cutting oil, drawing compound, rust preventative, heat-treat scale, laser-cut oxide, weld spatter and buffing compound all come off first, and each needs a different removal step — which is why the substrate and its history belong on the paperwork. A carburised part, a welded part and a screw-machine part do not get the same cleaning cycle.
Then activation: an acid step that takes off the last oxide and leaves a surface the deposit can bond to. Stainless needs its passive layer stripped and usually a nickel strike straight afterwards, because the oxide reforms in seconds. Aluminum needs a zincate. Heat-treated and high-alloy steels need their own activation, and getting it wrong shows up as blistering weeks later rather than as a reject at the tank.
Plating also replicates the surface it lands on. It does not fill machining marks, porosity or pits, and a bright deposit makes them more visible, not less. If the incoming surface needs work, that is a separate operation — media blasting for scale, oxide and a uniform matte texture, or mechanical finishing before the part reaches a line.
Acid cleaning and electroplating both generate atomic hydrogen at the part surface, and some of it diffuses into the steel. In high-strength steel under sustained load, that hydrogen concentrates at stress risers and cracks the part — hours or days later, with no warning and no visible cause.
The trigger is strength, not the coating. ASTM B633 draws the line at 1000 MPa ultimate tensile, roughly 31 HRC, and adds surface-hardened parts — carburised, nitrided, induction-hardened — regardless of core strength. Above that line, embrittlement relief baking is required.
Timing is what people get wrong. The bake starts within four hours of the part leaving the last process, and it happens before any chromate or passivate, because those films are heat sensitive and a bake damages them. The longer hydrogen sits in the lattice, the less of it comes back out, so a load that waits overnight has not been relieved by baking it the next morning. The schedule itself is not printed in B633; it comes from ASTM B850, keyed to tensile strength and part class. Where a specification calls for proof, ASTM F519 is the test method. Stripping and replating restarts the clock — a reworked part needs the bake again.
What this means for a drawing: state the substrate, the heat treat condition and the hardness or tensile strength. No shop can infer strength from a part’s appearance, and a part that arrives without it either gets baked unnecessarily or does not get baked at all. Neither is acceptable on aerospace or defense hardware.
Most of what reaches us is a specification question rather than a process question. These references answer the document first, then say what we do about it.
ASTM B633 — service conditions SC 1 to SC 4, Types I to VI, which types are hexavalent, the RoHS question, and how to write a callout a shop cannot misread.
QQ-S-365, ASTM B700 and ASTM B488 — type, grade and class for silver, gold codes and thickness classes, and what happened when QQ-S-365D was canceled.
ASTM B733 — phosphorus classes, thickness grades, post-plate heat treatment, and what the class actually changes about the deposit.
AMS-QQ-P-416 — types and classes, the embrittlement requirements that travel with the specification, and the conversion question.
Where a part needs a plated finish plus chem film, a dry film lubricant topcoat or paint, plating and coating under one roof explains how that gets sequenced without shipping parts between vendors. Certificates are listed under certifications, and the export-control position under ITAR registered.
The process set is split across sites deliberately rather than duplicated. Where a job runs is part of the answer, and it is worth knowing before the purchase order.
2220 Grisham Drive. Alkaline zinc, black zinc, matte tin, yellow chem film, citric passivation, zinc phosphate, dry film lubricant and the full anodize color range. See Rowlett and Dallas-Fort Worth metal finishing, or zinc plating in Dallas.
3800 W Ursula Avenue. Cadmium, gold, sulfamate nickel, bright and semi-bright silver, and Type III hardcoat anodize. See McAllen and Rio Grande Valley metal finishing.
Copper is never quoted as a standalone finish — undercoat only. If a process you need is not on either list, ask rather than assume; the answer is a plant, a partner, or an honest no.
Gleco Plating is a family-owned metal finishing company in Texas, founded in 1979, running plating plants in Rowlett and McAllen alongside a paint and powder coating facility in Rowlett.
We hold AS9100D and ISO 9001:2015. The AS9100D certificate covers three sites. We are ITAR registered, DFARS compliant and RoHS compliant. We are not Nadcap accredited, and we would rather say that here than have you find it in an audit.
We do not do chrome plating — not hard chrome, not decorative. When a print calls for it the useful question is what the chrome was for: wear and hardness usually route to electroless nickel on steel or Type III hardcoat on aluminum, and appearance usually routes to bright nickel or bright tin. We also do not quote copper as a final finish.
Everything else on this page runs in house, to print, with the certification package the specification calls for. Work is organized by acceptance criteria as much as by process, because electronics, automotive and heavy truck, medical device and industrial and energy requirements differ more than the tanks do.
How the part is held. In barrel plating parts go loose into a rotating perforated drum and make contact by tumbling — cheap, suited to small robust hardware in volume, with no individual handling. In rack plating each part is fixtured in a fixed position relative to the anodes, which lets you control thickness distribution, shield hot edges and drive current into recesses, at higher cost and with a contact mark wherever the fixture touched. Size, weight, thread criticality and cosmetic requirement decide it.
On a flat face, the deposit thickness. On a diameter or a bore, twice that, because it lands on both sides. On a 60° thread, pitch diameter grows by roughly four times the plating thickness — that is the one that catches people out. Current density also runs high at edges and corners, so those carry more deposit than the middle of a face. If a feature cannot grow, mask it or dimension it to accept the build, and say which on the drawing.
Yes, with a different front end. Stainless carries a passive chromium oxide film that nothing bonds to, so it has to be removed and the surface activated, usually with a nickel strike applied immediately because the oxide reforms in seconds. Worth asking first, though: if the requirement is corrosion resistance on stainless, passivation to remove free iron is often the correct and cheaper answer. If it is solderability, conductivity or a specific contact surface, plating is the answer.
If the steel is above roughly 1000 MPa ultimate tensile — about 31 HRC — yes. If it is surface hardened by carburising, nitriding or induction, yes, regardless of core strength. The bake starts within four hours of the part leaving the last process and happens before any chromate or passivate, because those films are heat sensitive. Temperature and duration come from ASTM B850, keyed to tensile strength and part class. Put the substrate, heat treat condition and hardness on the drawing.
Usually zinc with a trivalent chromate, called to ASTM B633 at the service condition matching the environment — the service condition, not the chromate color, is what sets the protection. If zinc will not reach the hours, the next step is zinc-nickel, which corrodes far more slowly, survives heat far better and is the standard answer for road salt, marine exposure or an assembly bolted to aluminum. It costs more. We will not quote you an hour figure here: the hours are set by the specification revision on your drawing, so send the callout.
No — neither hard chrome nor decorative. The follow-up matters more than the answer, because chrome on a print is usually standing in for something else. For wear resistance and hardness, electroless nickel on steel or Type III hardcoat anodize on aluminum normally covers it, and electroless nickel has the advantage of depositing uniformly in bores and blind features. For appearance, bright nickel or bright tin is the usual substitution. Send the print and tell us what the chrome was doing.
Yes, with a zincate. Aluminum reoxidises instantly in air, so nothing bonds to it directly; a controlled zinc displacement layer goes down first and the deposit goes on top. It works, but it adds steps and it is unforgiving of wrong alloy or temper information. If the goal is hardness or corrosion resistance rather than conductivity or solderability, anodizing is usually the better and cheaper route.
It depends on the process. Cadmium, gold, sulfamate nickel, bright and semi-bright silver and Type III hardcoat anodize run at McAllen. Alkaline zinc, black zinc, matte tin, yellow chem film, citric passivation, zinc phosphate, dry film lubricant and the full anodize color range run at Rowlett. Paint, powder and Cerakote run at the Paint & Powder facility in Rowlett. If your part needs two processes that live at different sites, say so up front and we will route it rather than surprise you with a transfer.
Send the print. Tell us the substrate, the heat treat condition and what the coating has to survive, and we will tell you which deposit, rack or barrel, and which plant.
Precision metal finishing since 1979. Plating, anodizing, coatings and passivation from three Texas facilities.
Our paint, powder & Cerakote division: Gleco Paint & Powder Coating
Gleco Rowlett
2220 Grisham Drive
Rowlett, TX 75088
972-475-4300
Gleco McAllen
3800 W. Ursula Ave
McAllen, TX 78503
956-800-4069
