ChromeVert™ Corrosion and Abrasion Characteristics
Corrosion test methods conform to ASTM B117 salt fog for the corrosion, with reporting based on ASTM B 537.
Table 1 shows the relative corrosion resistance of ChromeVert™ compared to chromium. Ten samples each of ChromeVert™ and chromium are plated 10 millionths of an inch over 300 millionths of an inch of bright, electrolytic nickel. This is a typical plating specification for corrosion resistance.
The samples are exposed to a salt fog for a duration of 264 hours under the following conditions:
- Salt concentration in water: 5%
- Concentrate delivery to specimens per hour: 1.9 milliliters per hour +/1 0.1 ml/hr
- Duration of test: 264 hours
- Chamber temperature: 100F +/- 2F
- Chamber pressure: 13.5 PSI +/- .5 PSI
Each specimen is reviewed at 24-hour intervals for degree of corrosion and graded according the Protection Rating panels 1-9, as supplied from ASTM B117-03. The following photos show panels 1-9.
Table I Relative Corrosion Resistance of ChromeVert™ vs Chromium
|Sample ID||1||9R||9R||8R||8R||8R||8R||7R||7R||-||-||-||ChromeVert / nickel|
|2||9R||9R||9R||9R||9R||9R||9R||9R||9R||9R||9R||ChromeVert / nickel|
|3||9R||9R||8R||7R||6R||-||-||-||-||-||-||ChromeVert / nickel|
|4||9R||9R||9R||9RW||8RW||8RW||8RW||7RW||6RW||-||-||ChromeVert / nickel|
|5||9R||9R||9R||8R||6RW||-||-||-||-||-||-||ChromeVert / nickel|
|6||9R||8R||7R||6RW||-||-||-||-||-||-||ChromeVert / nickel|
|7||9R||8R||8R||8RW||7RW||6RW||-||-||-||-||-||ChromeVert / nickel|
|8||9R||9R||9R||8R||8R||8R||7R||7RW||6RW||-||-||ChromeVert / nickel|
|9||9R||9R||8R||7R||6R||-||-||-||-||-||-||ChromeVert / nickel|
|10||9R||9R||9R||8R||8R||6R||-||-||-||-||-||ChromeVert / nickel|
|11||7R||7R||6RW||-||-||-||-||-||-||-||-||Chromium / nickel|
|12||7R||6R||-||-||-||-||-||-||-||-||-||Chromium / nickel|
|13||8R||8RW||6RW||-||-||-||-||-||-||-||-||Chromium / nickel|
|14||8R||6R||-||-||-||-||-||-||-||-||-||Chromium / nickel|
|15||8R||8R||8RW||7RW||6RW||-||-||-||-||-||-||Chromium / nickel|
|16||8R||8R||6RW||-||-||-||-||-||-||-||-||Chromium / nickel|
|17||9R||9R||8RW||6RW||-||-||-||-||-||-||-||Chromium / nickel|
|18||9R||8R||7RW||6RW||-||-||-||-||-||-||-||Chromium / nickel|
|19||9R||7R||6R||-||-||-||-||-||-||-||-||Chromium / nickel|
|20||8R||8R||6RW||-||-||-||-||-||-||-||-||Chromium / nickel|
|Chromium / nickel|
R = Rust stain
W = White stain
Corrosion Test Summary
These tests show that the ChromeVert™ plating with a thickness of 10 millionths (0.000010”) of an inch deposited on 300 millionths (0.000300”) inch of bright, electrolytic nickel has more than twice the salt spray hours as conventional decorative chromium (also 10 millionths over 300 millionths).
Abrasion Test Apparatus and Materials
An Abrasion Tester, as illustrated in Fig. 1 and Fig. 2, was used. A gate for starting the flow of abrasive is located near the top of the guide tube. It has a metal disk inserted into a slit in the side of the guide tube with a collar covering the slit. The guide tube is firmly supported in a vertical position over a suitable receptacle, which contains a support for holding the coated panel at an angle of 45° to the vertical. The opening of the tube is directly above the area to be abraded. The distance from the tube to the coated surface face at the nearest point is 25 mm (1 in.) when measured in the vertical direction. The base of the apparatus is fitted with adjusting screws for properly aligning the equipment.
The standard abrasive is natural silica sand from the St. Peters or Jordan sandstone deposits (located in the central United States). It is considered “standard” when graded as follows after 5 min of continuous sieving.
- 0 % retained on a No. 16 (1.18 mm) sieve
- Maximum 15 % retained on a No. 20 (850 µm) sieve
- Minimum 80 % retained on a No. 30 (600 µm) sieve
- Maximum 5 % passing a No. 30 (600 µm) sieve
The sand is characterized by its roundness of grains and has silicon dioxide content greater than 99 %. Use the sieves described in Specification E 11.
Note 1: The abrading qualities of sand obtained from different sources may differ slightly even though the s and meets the sieve requirements. Therefore, for maximum precision of test results, purchaser and seller should use sand from the same source.
Test Specimens Both sample groups are plated with 10 millionths of an inch of ChromeVert™ or chromium, over 300 millionths of an inch of bright, electrolytic nickel. This is a typical plating specification for corrosion resistance. Five samples of a chromium/nickel construction were compared to 19 samples of the ChromeVert™/nickel construction. Table II on page 6 shows the individual results.
TABLE I - ChromeVert™ Plating Wear Resistance Properties
|The test methods used conform to ASTM B 117/537. The abrasion test used is a modified version of ASTM D 968 ( ASTM D 968-8) using 20 liters of sand instead of 100. The two ASTM specifications are partial fulfillment of the requirements of SAE Aerospace Standard AS4984.|
|AL ID No.||SOT ID No.||Original Weight (g)||End Weight (g)||Weight Loss (g)||Liters of Sand||Comments|
|Ni/Cr X = 0.9 mg||s = 0.0004|
|Ni/Sn/Co X = 0.8 mg||s = 0.0007|
Abrasion Test Summary
The weight loss of the ChromeVert™ deposit was an average of 0.8 mg versus 0.9 mg for chromium. This test shows that ChromeVert™ is in a comparable range of wear, even though it is not quite as hard as chromium. Previous testing has shown that ChromeVert™ deposits are about 70% the hardness of chromium, which is about equal to bright nickel. In most cases, this is an acceptable level of abrasion resistance to justify a switch from chromium to ChromeVert™ plating.