Better Chemistry. Better Business.


Increase salt spray protection by 50% without any capital expenditure.

Tru-Line Manufacturing: Decatur, Alabama

truline manufacturing sign

1. Background

Established in 1976, Tru-Line Manufacturing has become a leading fabricator of steel hydraulic lines for use in heavy equipment, utility tractors, golf/turf equipment and similar OEM products. Additionally, the company fabricates structural metal tubing and offers powder-coating services for products fabricated within the company, as well as those produced by other companies.

Tru-Line Manufacturing has grown from a 10,000 square foot Quonset hut to a 100,000 square foot manufacturing facility, including a 25,000 square foot powder-coat process line. The company has expanded its service lines to include advanced CNC tube bending, contract powder coating and recently introduced their own line of “Made in America” tree stands and accessories for hunting enthusiasts under the label.

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2. Problem Definition

One of Tru-Line’s largest customers requires at least 96 hours of ASTM B-117 salt spray protection on bare steel tubing as specified by an original equipment manufacturer. Faced with the inability to meet corrosion.and salt spray testing requirements, Tru-Line Manufacturing needed some answers. When Tru-line’s existing supplier failed to solve the problem, Rhonda Fiske, Tru-Line’s Quality Assurance Manager reached out to Hubbard-Hall’s Technical Service Group and Manager Larry Ensley to evaluate the situation.

Based on Hubbard-Hall’s experience, they decided to utilize a combination of products that have successfully increased salt spray protection for several other similar applications. By applying Metal Guard 510 over Hubfos 150, Tru-Line exceeded its customer’s requirements. Next up were Tru-Line’s phosphate lines. Hubbard-Hall successfully converted a six-stage spray iron phosphate line, three Niagara tube washers and a seven-stage immersion iron phosphate line with the following process: Alkaline cleaner – Lusterclean 11-L, Descaling bath – Ahcophos 12, Iron phosphate – Hubfos 150, Rust preventative – Metal guard 510.

masking plug close up

Steel hydraulic tubes prior to the phosphate pre-treatment line

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Manual powder is sprayed as a touch-up in the spray booth


Freshly powder-coated steel hydraulic tubes

3. Additional Challenges Provide More Opportunities

The majority of Tru-Line’s business is in fabricating carbon steel and aluminum fluid transfer lines, requiring 3,000 – 4,000 PSI of pressure from ¼” to 2 ½” tubing. A major concern is protection from flash rust and short term storage. Eighty percent of their finished products are powder coated to meet customer requirements. Advantages of powder coating include: an environmentally friendly coating with no hazardous air pollutants (HAPs) or volatile organic compounds (VOCs), in addition to minimizing the costly disposal of carrier solvents and paint waste. Unpainted fabricated tubes require at least 96 hours of salt spray protection in accordance with ASTM-B-117 specifications before the first rust occurs.

Due to Tru-Line’s success in solving the bare steel salt spray problem, the company was presented a tougher challenge by the same large account; increase ASTM D-1654 paint adhesion results from 240 hours to 500 hours. To meet this new requirement, it tested various iron phosphate and non-chrome, pre-paint chemicals from several national suppliers, and was able to achieve greater than 500 hours of paint adhesion with several non-chrome chemistries, including Hubbard-Hall’s Emerald Paint Prep 390 LT. However, the decision was made to stay with Hubbard-Hall’s iron phosphate, Hubfos 150, and use the non-chrome sealer, Emerald Seal 308.

The benefit: Tru-line was able to use existing equipment and process parameters. The only change required was the replacement of the existing non-chrome sealer with Emerald Seal 308. The use of Hubfos 150 with the Emerald Seal 308 allowed Tru-line to achieve 750 to 800 hours of ASTM D-1654 paint adhesion, surpassing the 500 hour requirement without any capital expenditure. Hubbard-Hall has been able to duplicate these paint adhesion results at several different metal fabricators and powder coaters by taking advantage of the synergy achieved when using Hubfos 150 with the Emerald Seal 308.

Paint Prep results

 4. Testing Procedures and Analysis: Evaluation of Painted/Coated Panels Subjected to Salt Spray Environment

Lab Testing procedures

Received two sets of panels run in a trial at Tru-Line using Emerald Paint Prep 390 LT prior to powder coating.

  1. Hubfos 150 with non-chrome sealer (Panels 1 -4)
  2. Hubfos 150 with Emerald Seal 308 (Panels 5 – 8)

Panels were scribed and subjected to ASTM B-117 salt spray testing per ASTM D-1654 paint adhesion test.

Periodically, creepage was measured from the scribe line. All panels processed with Hubfos 150 in addition to different sealers.

214 cropped5. Results

Tru-Line Mfg. worked closely with Hubbard-Hall to fine tune the process, achieving results far beyond what the company thought possible. As Rhonda
Fiske put it: “The confidence I have in Hubbard- Hall is reinforced by everyone I meet at Hubbard- Hall.”

The ability to analyze the issues that were specific to Tru-Line was a refreshing change from other suppliers. The knowledge and ability displayed by Hubbard-Hall’s technical team provided Rhonda’s team with realistic solutions that were readily adopted. Tru-Line is now looking at other finishing processes in which Hubbard-Hall may be able to improve the company’s productivity.

6. Phosphate Process

6 Stage Spray Phosphate Process Hubbard-Hall Products/Solutions

1st Stage – Alkaline Cleaning

The 1st Stage is a high temperature alkaline cleaner designed to remove oils and organic contaminates from the surface of the metal.

Aquaease SL 916

  • Operating temperature – 140⁰F
  • Operating solution – 5% by volume

2nd Stage – Water Rinse

3rd Stage – Iron Phosphate

The 3rd Stage is the application of Iron Phosphate. This provides an organic accelerated iron phosphate coating prior to powder coating.

Hubfos 150

  • Operating temperature – 130⁰F
  • Operating solution – 3% by volume

4th Stage – Water Rinse

5th Stage – Final Seal

The 5th Stage is a final seal for pretreatment systems to produce a corrosion resistant, adhesion promoting metal surface profile, to enhance the bonding of most organic finishes to the treated parts.

 Emerald Seal 308

  • Operating temperature – 100⁰F
  • Operating solution – 0.5% by volume

6th Stage – Halo Water Rinse