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Zinc Sealing & Corrosion ProtectionTECHNICAL RESOURCE
Home ／ GT-Sealer 501HT
Black coated flange screws sealed with GT-Sealer 501HT
Black coated fasteners: the case where dehydrogenation and the sealer film have to coexist.
PRODUCT PROFILE

GT-Sealer 501HT

A water-based organic-inorganic sealer. The datasheet states no discolouration at 250 °C and corrosion resistance retained after dehydrogenation — the property that allows a single-step seal-then-bake route for high-strength fasteners.

250 °Cno discolouration
100–400ml/L working range
0.13–0.18friction coefficient
Request TDS / sample Parameters

This site does not sell the product or quote prices. Samples and technical documents are handled by the manufacturer or its authorised channel.

What it is designed to solve

High-strength fasteners are baked after plating — 190–220 °C for hours to more than twenty hours. Most sealing films do not survive that. 501HT's datasheet states no discolouration at 250 °C, with corrosion resistance retained after dehydrogenation, which is what makes the seal-then-bake route viable.

Beyond heat resistance, the published profile is balanced rather than extreme: good salt spray, stable friction (0.13–0.18), good coverage, a hard and abrasion-resistant film. Combined with a 100–400 ml/L working range and a bath that needs no heating, no pH adjustment and no continuous agitation, the total cost of use is low. Field results vary with coating, passivation and part geometry — validate on your own parts.

Boundary: 250 °C is not a salt-spray guarantee. Achievable hours depend on zinc thickness, passivation, film weight, geometry and test standard. Validate any process change on a small batch first.
Parameters (from the TDS)
ProductGT-Sealer 501HT high-performance water-based sealer
TypeOrganic-inorganic water-based sealer
SubstratesZinc / zinc-nickel / zinc-iron / zinc-cobalt / zinc alloys / aluminium (after trivalent passivation)
Heat resistance250 °C no discolouration; corrosion resistance retained after dehydrogenation
Working concentration100–400 ml/L
Operating temperatureAmbient – 40 °C
pH7.5–10 (no routine adjustment, top up with concentrate)
Friction coefficient0.13–0.18
AppearanceSilver-white after blue-white or yellow passivation

Bath make-up and maintenance

StagePractice
Make-upMix to the target concentration within 100–400 ml/L. Start at the lower end and run a gradient to find the minimum effective concentration — thicker films carry higher internal stress.
MaintenanceWithin pH 7.5–10 no adjustment is normally needed; top up with concentrate as the level drops. No continuous low-shear mixing and no 80–150 µm filtration.
TemperatureAmbient to 40 °C, no heating required — for a small plating shop this removes a year-round electricity cost and a temperature control loop.
DrainingThread roots, blind holes and overlapping faces are where coverage fails. Improve racking and drip time before increasing concentration.
DryingDry to the film-forming conditions in the TDS; do not confuse this step with dehydrogenation.

Frequently asked questions

QuestionAnswer
Can 501HT be dropped into an existing bath as a direct replacement?No. Change of chemistry requires cleaning or a transition procedure, and a small-batch validation on your own parts — salt spray and appearance in particular. Ask the supplier for the written change-over procedure.
Does 250 °C mean the part will pass 96 h salt spray?No. Heat resistance and corrosion resistance are separate properties. 250 °C describes film behaviour under bake; salt-spray hours also depend on zinc thickness, passivation, film weight and the test standard.
Which concentration in the 100–400 ml/L range should we use?It depends on substrate, coating and salt-spray requirement. Start low and run a gradient: find the lowest effective concentration that meets the acceptance criterion. Higher concentration means a thicker film and higher internal stress.
Does the bath need heating or agitation?The datasheet states ambient to 40 °C, pH 7.5–10 with no routine adjustment and top-up with concentrate only — no continuous low-shear mixing and no 80–150 µm filtration.
Can it be used on zinc-nickel?Yes. Substrates include zinc-nickel, zinc-iron, zinc-cobalt, zinc alloys and aluminium after trivalent passivation. Zinc-nickel parts are usually automotive, so validate against the OEM standard.
Are test reports and SDS available?Technical datasheet and application documentation are available. This site does not sell the product; request documents through the enquiry form and they will come from the manufacturer or authorised channel.

Appearance systems

The same sealer looks different over different passivation systems. These are the common appearance targets used when agreeing a standard with a customer.

BRIGHT Bright silver sealed wheel bolts
Bright silver: achievable after blue-white or yellow passivation; requires uniform colour and no runs.
SILVER ZINC Silver white zinc plated wheel bolts
Silver-white zinc: the usual appearance grade for automotive and wheel fasteners.
COMPARISON Fasteners with different coating and sealing combinations
Different coating × sealing combinations: appearance and corrosion resistance must be specified together.

Images are appearance references, not test reports. Actual appearance depends on substrate, coating thickness, passivation and drying conditions.

Request the datasheet or a sample

Tell us the substrate, passivation, salt-spray requirement and whether the part is baked. We will route the request technically.

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Disclaimer: this is an independent technical resource. Parameters are quoted from published product datasheets (TDS) with sources named, and are not extrapolated. Results vary with substrate, coating thickness, passivation system and equipment; validate any process change on a small batch first. We do not provide product quotations or sell chemicals.